LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 

Class 


MODERN 
STEAM    ENGINEERING 

BY  GARDNER   D.   HISCOX,   M.E. 


INCLUDING  AN  ELECTRICAL  SECTION 

BY   NEWTON    HARRISON,   E.E. 


MODERN 

STEAM  ENGINEERING 

IN   THEORY   AND    PRACTICE 


A  NEW,    COMPLETE,   AND  PRACTICAL  WORK  FOR 

Steam-Users,  Electricians,  Firemen,  and  Engineers 

CONTAINING  LATEST  PRACTICAL  INFORMATION  ON 

BOILERS  AND  THEIR  ADJUNCTS;  ECONOMY  OF  STEAM-MAKING  AND 
ITS  USE  FROM  THE  FUEL  TO  THE  CONDENSER,  WITH  ILLUSTRATED 
DETAILS  OF  STEAM  ENGINE  PARTS;  SUPERHEATED  STEAM,  ITS 
USE  AND  ECONOMY;  DETAILS  OF  SLIDE-VALVE  AND  HIGH-SPEED 
ENGINES;  CORLISS,  COMPOUND,  AND  TRIPLE-EFFECT  ENGINES;  THE 
STEAM-TURBINE  AND  ITS  WORK;  THE  COST  OF  STEAM  POWER, 
ITS  APPLICATION  AND  OPERATION  IN  POWER  PLANTS  FOR  ELEC- 
TRIC GENERATION,  PUMPING,  REFRIGERATION,  AND  ELEVATORS 

OVER  TWO  HUNDRED  QUESTIONS,  WITH  THEIR  ANSWERS,  LIKELY 

TO  BE  ASKED  BY  THE  EXAMINING  BOARDS  ARE  GIVEN,  AS 

WELL  AS   FORTY  TABLES   OF   THE   PROPERTIES  OF 

STEAM  FOR  POWER  AND   OTHER  USES 

BY 

GARDNER    D.    HISCOX,    M.E. 

Author  of  "Gas,  Gasoline,  and  Oil  Engines,"  etc. 
WITH   CHAPTERS   ON   ELECTRICAL  ENGINEERING   BY 

NEWTON    HARRISON,    E.E. 

Author  of  "Electric  Wiring,  Diagrams,  and  Switchboards" 
ILLUSTRATED    BY    OVER    400    SPECIALLY    MADE    ENGRAVINGS 


NEW    YORK 

THE    NORMAN   W.    HENLEY   PUBLISHING   COMPANY 

132   NASSAU    STREET 

1907 


OF  THE 
UN!  VFPR1TV 


COPYRIGHTED,  1906,  By 
THE  NORMAN   W.   HENLEY  PUBLISHING  COMPANY 


NOTE.— Each  and  every  illustration  in  this  book  was 
specially  made  for  it,  and  is  fully  covered  by  copyright. 


COMPOSITION,  PRINTING,   AND  ELECTROTYPING 
BY  THE  TROW   PRESS,   NEW  YORK,  V.  S.  A. 


OF  THE 

UNIVERSITY 


PREFACE 

IT  has  been  the  aim  of  the  author  in  the  production  of  this  work 
to  fully  meet  the  wants  of  the  student  and  engineer^in  all  the  prac- 
tical requirements  for  obtaining  a  mastery  in  the  application  and  use 
of  steam  for  power  and  other  purposes  in  the  full  range  of  its  use- 
fulness. 

A  further  object  has  been  to  bring  the  mathematical  side  of 
Steam-Engineering  into  such  practical  .conditions  that  the  engineer 
or  student  may  be  able  to  grasp  the  whole  subject  with  only  ordinary 
arithmetical  acquirements  by  means  of  the  figured  repetition  of  the 
formulas.  . 

In  the  forty-two  tables  included  will  be  found  a  ready  reference, 
covering  all  conditions  of  the  properties  of  steam  and  its  application 
for  the  production  of  power,  ratios,  engine  parts  and  proportions, 
most  useful  in  the  service  now  devolved  upon  the  duties  of  a  suc- 
cessful engineer. 

Owing  to  the  wide  experience  of  the  author,  who  well  knows  the 
points  a  book  like  this  must  cover  to  be  of  greatest  service  to  the 
men  for  whom  it  is  written,  he  has  treated  at  length  the  subject  of 
Superheated  Steam  and  the  practical  operation  of  the  Plain  Slide- 
and  Piston-Yalves  and  their  gear,  the  Corliss  Valves  and  valve-gear, 
also  the  Triple-  and  Quadruple-Expansion  Engine  and  the  work  of 
the  Indicator,  as  well  as  the  Steam -Turbine,  which  is  now  coming  to 
the  front  as  a  power-producer. 

The  duties  of  an  Engineer,  who  is  entrusted  with  the  management 
and  use  of  Steam  in  a  private  or  public  capacity,  are  given,  as  well  as 
chapters  on  Eefrigeration-Plants,  Elevators,  and  Electric-Light  Plants. 

Questions  as  asked  by  the  Examining  Board  are  included,  as  well 
as  their  answers,  which  will  prove  of  greatest  help  to  those  prepar- 
ing for  and  desiring  to  procure  a  License  as  a  Steam -Engineer. 

Much  time  has  been  spent  and  great  care  taken  in  the  prepara- 
tion of  this  work,  and  the  author  trusts  that  it  will  many  times  over 
compensate  the  reader  for  its  perusal. 

GARDNER  D.  Hiscox. 
NOVEMBER,  1906. 


CONTENTS 


CHAPTER   I 

PAGE 

Historical,  early  progress  of  the  steam-engine 15-23 

CHAPTER    II 

Steam  and  its  properties,  below  atmospheric  pressure ;  boiling  temperatures, 
elastic  force  of  vapor;  heat  of  evaporation  and  quantity  evaporated 
62°  to  212°;  boiling  fluids  above  212°;  boiling  in  vacuo;  salt-pan; 
sugar-pan — four  tables  .  .  .  •..'.-  .  .  .  .  .  24-30 

CHAPTER   III 

Generation  of  steam;  furnaces  and  their  adjuncts;  fuels;  wood,  coal,  lignite, 
turf,  •  coke,  sawdust,  bagasse,  straw,  petroleum,  gas ;  efficiency  and 
economy  of  fuels;  boiler-furnaces,  grate-bars,  stokers,  link-grates; 
liquid  fuel  trials ;  efficiency;  oil-burners  of  various  types,  one  table  31-48 

CHAPTER  IV 

Types  of  boilers;  Stevens,  cylinder,  flue,  tubular,  Galloway,  boiler-settings; 
internal-fired,  marine,  down-draught,  Herreshoff,  Thornycroft,  Wood, 
Du  Temple,  Cahall,  duplex,  Sterling,  Babcock  &  Wilcox,  and  vertical 
boilers ;  horse-power  rating  of  boilers ;  heating  and  grate-surface ;  table ; 
indicators  of  boiler-control,  safety-valve  areas  and  computation ;  lever 
safety-valve,  differential,  pop ;  quick-opening  water-gauge ;  recording- 
gauge;  fusible  plugs;  strength  of  boilers;  shell,  lap-joints,  proportions 
for  joints,  table;  hydraulic  test,  working  pressures,  stays,  braces, 
five  tables  .  .  .  . .  49-73 

CHAPTER  V 

Boiler-chimney  and  its  work ;  draught  formulas,  diagram,  draught-pressures, 
table ;  draught-gauge,  size  and  height  of  chimneys,  table,  steel  and  brick 
chimneys ;  firing  and  chimney-draught ;  forced-draught  steam-blowers, 
Korting  and  fan-blowers;  two  tables 74-83 

CHAPTER  VI 

Heat-economy  of  the  feed-water ;  saving  of  fuel,  table ;  tube-surface  of  heat- 
ers, table ;  formulas,  multicoil  heater,  open  heater,  Berryman,  Wain- 
wright,  Cookson,  filter,  and  Hoppes  heater;  Green  economizer,  two 

tables -       •       •     84-93 

9 


10  CONTENTS 

CHAPTER  VII 

PAGE 

Injector  and  steam-pump;  velocity  of  steam  and  water,  table,  formulas; 
Penberthy,  Little  Giant,  Lunkenheimer,  Metropolitan,  Korting,  and 
exhaust-injector,  efficiency;  steam-pump  and  its  work ;  pump-lift  heads, 
table;  cylinder-proportions,  formula  for  friction-head;  Knowles,  Worth- 
ington,  Deane,  Cameron,  McGowan,  Guild  &  Garrison,  and  Blake  pumps ; 
pump- valves;  strainers  and  air-chambers,  two  tables  .  .  .  94-110 

CHAPTER   VIII 

Incrustation  in  boilers  and  its  remedy;  boiler  compounds,  purification  of 
feed-water;  table,  purifying  apparatus;  standard  chemicals,  settling- 
tanks;  factor  of  evaporation,  table,  formulas;  the  jet-condenser,  siphon- 
condenser,  ejector-condenser,  water  required  for  condensing,  table, 
formula,  surface  and  combination  condensers;  concentric  tube  and 
spray-condensers;  exhaust-separators;  air-  and  circulating-pump, 
Edwards  air-pump ;  water-cooling  towers,  high- vacuum  installation  with 
cooling-tower,  three  tables 111-129 

CHAPTER   IX 

Steam  above  atmospheric  pressure,  diagram  of  steam-generation,  qualities 
of  steam,  specific  heat,  latent  heat;  formulas  and  examples,  critical 
temperature,  formulas  for  pressure,  temperature  and  volume  of  steam; 
examples,  ratios,  total  heat-units;  tables  of  the  properties  of  saturated 
steam,  one  table 130-139 

CHAPTER   X 

Flow  of  steam  through  orifices,  nozles,  and  pipes;  formulas  and  examples, 
straight  nozle,  expanding-nozle,  diverging  and  nozle  of  best  form; 
formulas  and  examples  for  velocity  and  dryness  of  steam;  table  of 
pressures,  -velocities  and  dryness  by  expansion,  value  of  x,  diagram  of 
theoretical  expansion-curves;  energy  of  steam;  flow  of  steam  through 
long  pipes ;  formulas  and  table ;  friction  and  loss  of  head,  two  tables  140-146 

CHAPTER   XI 

Superheated  steam  and  its  work;  generation,  economy,  expansion,  increased 
volume;  superheater,  cost,  action  in  cylinders,  in  turbines,  efficiency, 
specific  volume,  table,  formula  and  example,  consumption  by  super- 
heat for  power,  table;  tests  marine  and  locomotive,  tests  in  Europe; 
rescue  of  heat  from  the  chimney;  waste  of  heat  in  steam-making, 
specific-heat  formulas  and  examples;  table  of  total  heat;  superheaters 
and  their  construction ;  Buckley  and  Metesser  superheaters ;  rear  cham- 
ber, locomotive  and  separate  chamber  superheaters;  Schwoerer  and 
Foster  types;  Babcock  &  Wilcox  and  Schmidt  system;  management, 
factor  of  safety,  requirement  and  economy  of  superheaters ;  the  measure- 
ment of  steam,  sale  of  steam,  three  tables 147-170 


CONTENTS  11 

CHAPTER  XII 

PAGE 

Adiabatic  expansion  of  steam;  ratio  formulas,  exponents,  specific  heat  at 
constant  pressure,  constant  volume ;  dryness,  x,  formulas  and  examples 
for  y ;  table  of  real  cut-off,  values  of  real  cut-off;  formulas  and  examples 
for  mean  forward  pressure ;  table  of  cut-off  mean  pressures ;  terminal 
pressures,  formula,  example  and  table;  available  heat  in  steam,  in 
exhaust;  compressed  steam,  interchangeable  heat;  high-speed  engine- 
economy,  limit  of  pressure,  long  stroke,  overload, -tests,  leakage; 
theoretical  efficiency  of  the  steam-engine;  formula,  table;  actual 
efficiency,  formulas  and  examples;  compression  and  back  pressure, 
ratios,  experiments;  economy  of  high-pressure  steam,  diagrams; 
curves;  most  economical  point  of  cut-off,  diagram;  experiments,  four 
tables 171-189 

CHAPTER  XIII 

Indicator  and  its  work;  Lippincott,  high-pressure  piston,  reducing-wheel, 
setting  and  connections,  slack  spring,  right  and  left  indicator,  meas- 
urement of  card;  planimeters,  Amsler  and  Lippincott  application; 
water  used  per  h'orse-power  hour  by  diagram,  examples ;  high-compres- 
sion card ;  indicator-kinks,  admission  and  terminal  lines,  wavy  expan- 
sion-lines, diagrams  of  admission,  compression,  and  terminal  lines  and 
their  causes;  exhaust-lines 190-207 

CHAPTER  XIV 

Steam-engine  proportions ;  initial  condensation  formula,  cylinder,  diameters 
and  ratios  for  compound  engines,  triple-expansion  ratios;  thickness 
of  cylinders  and  heads,  bolts,  flanges,  clearance,  pipes,  ports,  valve- 
stem,  piston,  rings,  rod,  slides,  pins,  connecting-rod,  caps,  crank-pin, 
stresses,  crank,  rules;  shaft,  shaft-bearings,  fly-wheels,  rims  and  arms; 
speed,  table  of  high-speed  cylinder  dimensions;  table  of  slow-speed 
dimensions;  composite  pistons,  segmental  piston,  Harris,  Hewes  & 
Phillips  pistons ;  cross-heads,  connecting-rod  boxes,  main  bearings, 
fly-wheel  construction,  speed  formula,  weight,  table  of  safe  speeds, 
connecting-rod  angle,  three  tables 208-232 

CHAPTER  XV 

Slide  valve  and  valve  gear;  D  valve,  "over  and  under"  running  diagrams, 
valve  setting,  lap  and  lead,  table  of  changes  in  lap,  travel  and  lead, 
excessive  compression,  balanced  valves,  double  ported  and  riding 
cover  valves;  independent  cut-off  valves,  union  and  oscillating  valves, 
gridiron  valves ;  diagrams  of  lap,  lead  for  slide  valve  cut-off,  universal 
valve  diagram  for  measurement ;  piston  valve;  Noye,  hollow  piston, 
Armington  &  Sims,  Harrisburg  types;  slide  valve  gear,  link  motion 
gear,  Stephenson  and  variable  links,  Marshall  valve  gear ;  reversing  and 
floating  valve  gear,  Walscheart  valve  gear,  three  cylinder  and  Brother- 


12  CONTENTS 


hood  engine  valve  gear,  Wolf  and  triple  expansion  engine  valve  gear 
from  single  eccentric ;  Joy  and  Porter- Allen  valve  gear,  Ball  high  speed 
tandem  engine  and  valve  gear,  one  table  .......  233-266 

CHAPTER  XVI 

Corliss  engine;  illustrated  type,  valve  movements  and  gear,  single  and 
double  port  valves,  single  eccentric  valve  gear,  links  and  wrist  plate; 
double  eccentric  wrist  plates  and  valve  gear;  Fisnkill,  valve  gear, 
diagrams  of  piston,  crank  and  eccentric  positions  for  cut-off;  bell  crank 
knock-off,  Bass,  Allis-Chalmers,  Nordberg  and  trip  valve  gear;  Sioux 
City,  Scottdale  and  Watts-Campbell  valve  gear;  governors  and  dash 
pots;  Porter- Allen,  Watertown,  Lane  &  Bodley  and  Scottdale  governors; 
flywheel  and  pulley  governors;  Sweet,  Fitchburg,  shifting,  rotating, 
dash  pot  and  inertia  governors;  dash  pots;  Frick,  and  cup  cylinder 
types;  setting  Corliss  valve  gears,  wrist  plate  and  rocker  arm,  wrist- 
plate  positions;  table  of  lap,  lead  and  exhaust  release;  engines  of  the 
Hamilton,  tandem  compound  and  Cooper  model;  right  and  left  hand 
engines,  one  table 267-291 

CHAPTER  XVII 

Compound  engines;  loss  by  cylinder  condensation,  table,  value  of  com- 
pounding, table  of  water  consumption  in  single  and  compound  engines; 
experiments,  250  and  1,000  Ibs.  pressure;  cylinder  proportions,  ta- 
ble, Harrisburg  tandem  compound,  Vauclain  compound  and  balanced 
engine,  convertible  and  duplex  compound,  indicator  diagrams,  West- 
inghouse  compound  and  diagram ;  diagrams  of  steam  consumption  and 
efficiency  in  compound  and  non-condensing  engines;  receivers  with 
diagrams  of  pressures  under  variable  conditions;  reheating  in  receivers, 
three  tables 292-307 

CHAPTER  XVIII 

Triple  and  quadruple  expansion  engines;  increased  efficiency  by  multi- 
expansion  ;  table,  water  consumption,  test  of  high  duty  engine,  diagram 
of  pressures  and  temperatures;  cylinder  arrangement,  cylinder  propor- 
tions; engines  of  the  Montana,  Minnesota,  novel  marine  engine,  duplex 
piston  {riple  expansion  engine,  one  table 308-316 

CHAPTER  XIX 

The  steam  turbine;  progress;  Avery,  De  Laval  and  Parsons  type  described, 
bucket  type,  side  nozle,  steel  disk,  governing;  diagram  of  efficiency, 
velocities,  plan  of  De  Laval  turbine ;  Dow  and  Wilkinson  turbine ;  multi- 
stage turbine;  balancing  pistons,  form  of  blades;  Westinghouse  model, 
thrust  bearings,  admission  ports,  governing,  steam  puffs  or  vibrating 
inlet,  pilot  valve;  friction,  energy;  table  of  efficiency  tests,  governor 


CONTENTS  13 

PAGE 

and  vibrating  valve,  diagram  of  puffs,  Curtiss  turbine,  two  stage,  three 
stage,  arrangement  of  nozles  and  blades,  bucket  segment,  elevation  and 
plan  of  2,000  kilowatt  turbine,  slide  valve  regulation,  four  stage  tur- 
bine, shaft  step  details,  Rateau  turbine,  details  of  construction; 
Zoelly  turbine,  multistage  impulse  type,  details  of  wheel  and  guide 
disks — rotary  engine;  Dake  engine;  starting  and  operation  of  large 
steam  plants;  comparison  of  times  for  starting  to  full  speed,  suggestions, 
one  table 317-347 

CHAPTER  XX 

Mechanical  refrigeration  engineering ;  principles  of  refrigeration ;  ammonia, 
anhydrous  ammonia  and  its  properties,  compression  system;  table  of 
properties,  ammonia  receiver,  heat  interchange,  suction  and  discharge 
valves  and  their  action,  pressures  of  discharge  and  suction,  diagram 
of  principles,  latent  heat,  test,  liquid  only  that  absorbs  heat,  com- 
pressor, three  stages  of  refrigeration,  complete  refrigerating  plant ;  De 
La  Vergne  and  Frick  cylinders,  operation  of  the  cylinder  valves,  surface 
condenser,  double  pipe  condensers,  diagram  of  ammonia  compression ; 
pointers  on  the  operation  of  ammonia  plants,  pressures  and  economies, 
leaks,  ice  making,  expansion  valve,  charging  and  starting,  discharging 
air,  signs  of  healthy  working,  one  table 348-371 

CHAPTER  XXI 

The  elevator  and  its  working;  direct  cable,  hydraulic  piston  elevators,  pres- 
sure tank  plant,  high  lift,  multiple  lift,  three  way  valve,  pilot  valve, 
governor,  gravity  safety  apparatus,  automatic  control,  gravity  wedge, 
details  of  cylinder  and  valves  with  names  of  parts;  vamp,  escalator, 
worm  screw  elevator,  pump  pressure  regulator;  air  compressors  and 
compressed  air;  diagrams  of  compression  and  expansion,  two  stage 
compression,  compressors  of  the  Clayton,  Corliss,  Bennett,  Ingersol- 
Sergeant  types,  cylinders  and  valves,  four  stage  compressor ;  blowing 

Q7O_QQQ 

engines  ' o/-  a 

CHAPTER  XXII 

Cost  of  power;  economy,  table;  estimate  of  cost  of  power  plant,  table; 
cost  of  steam  per  horse  power,  table,  operative  expenses;  diagram  of 
condensing  plant,  diagram  of  non-condensing  plant ;  cost  of  distribu- 
tion, economical  suggestions  in  the  generation  and  use  of  steam,  boilers, 
pressures,  furnaces,  feed  water;  types  of  engine,  load,  overload,  losses; 
heating,  three  tables 390-399 

CHAPTER  XXIII 

The  engineer  and  his  duties,  reference  to  special  books,  license,  State  and 
local,  knocking  and  noises  in  the  engine  and  their  causes;  don'ts  for 
engineers  and  firemen ;  questions  and  answers  ....  400-414 


14  CONTENTS 


CONTENTS  OF  ELECTRICAL  SECTION 


CHAPTER  XXIV 

PAGE 

The  dynamo  and  its  regulation;  operation  of  the  dynamo;  generation  of 
E.  M.  F. ;  regulation  of  the  dynamo ;  regulation  with  a  rheostat ;  use  of 
the  commutator;  regulation  with  a  series  wound  dynamo;  classification 
of  dynamos;  regulation  in  a  shunt  wound  dynamo;  regulation  in  a 
compound  wound  dynamo 419-429 

CHAPTER  XXV 

Testing  and  motors;  testing  a  dynamo  for  faults;  causes  of  sparking;  use  of 
pole  spray;  short  circuiting  of  commutator  bars;  dynamo  fails  to 
generate ;  cause  of  heat  in  the  armature ;  heat  in  the  commutator  and 
brushes;  radiating  surface  of  coils  and  current  carrying  parts;  types  of 
motors  in  service;  sparking  in  the  motor;  the  back  E.  M.  F.  of  a  motor; 
humming  and  other  noises  in  a  motor  .  .  .  .  .  430-440 

CHAPTER  XXVI 

The  switchboard  and  storage  batteries;  centers  of  distribution;  classifica- 
tion of  circuits;  switchboard  appliances;  the  ground  detector;  the  light- 
ning arrester;  storage  batteries ;  types  of  storage  batteries;  difficulties 
with  plates;  efficiency  of  storage  cells;  the  battery  room  .  .  441-453 

CHAPTER  XXVII 

Lighting  and  lamps;  electric  lamps;  the  incandescent  lamp;  lamp  efficien- 
cies; the  Nernst  lamp;  the  open  arc;  the  flaming  arc  lamp;  the  en- 
closed arc;  the  mercury  vapor  lamp;  vacuum  tube  lighting;  electric 
light  equipments ;  steam  electric  plants ;  net  result  in  light  from  coal 
consumption;  water  power  plants ;  gas  engine  electric  plants  .  454-477 

Questions  and  answers  on  Chapter  XXIV 465 

Questions  and  answers  on  Chapter  XXV 467 

Questions  and  answers  on  Chapter  XXVI 470 

Questions  and  answers  on  Chapter  XXVII 473 


CHAPTER    I 


INTRODUCTION — HISTORICAL 

STEAM  has  been  known  as  a  source  of  power  since  the  earliest 
historic  time. 

It  lifted  the  cover  of  the  boiling-pot,  even  with  a  stone  upon  it, 
through  the  patriarchal  ages,  and  later,  with  a  tight-covered  boiler, 
as  designed  by  Heron  of  Alexandria,  it  became  a  source  of  power 
for  motion  in  a  rotary  engine  and 
in  lifting  a  ball  in  a  jet  of  steam,  as 
here  illustrated.  Steam  as  a  mo- 
tive force  appears  to  have  been 
well  known  to  the  priesthood  and 
magicians  of  Egypt  as  described  in 
their  incantations  for  creating  awe 
and  fear  in  the  ignorant  and  super- 
stitious people  in  that  benighted 
age.  There  are  reasons  for  believ- 
ing that  the  expansive  force  of  the 
steam  that  was  evolved  in  heat- 
ing the  immense  volumes  of  water 
for  the  hot  baths  at  Rome,  was  employed  to  elevate  and  discharge 
the  contents  of  the  boilers;  such  being  indicated  by  the  investiga- 
tions at  Pompeii. 

Steam  was  used  in  a  feeble  way  by  pressure  and  condensation 
for  raising  water  during  the  first  fifteen  centuries  of  the  Christian 
era,  when  its  coming  power  only  then  began  to  enlighten  the  in- 
dustrial horizon  as  the  dawn  of  its  brilliant  day  four  hundred  years 
later. 

The  experimental  development  of  the  properties  and  power  of 
steam  during  the  sixteenth  century — the  steam-played  organ  of 
Gerbert,  the  steam-gun  of  Leonardo  da  Vinci,  the  steam-boat  of  Blasco 
de  Garay,  the  steam  water-elevators  of  Baptist  Porta — was  a  prog- 

15 


Force  of  the 
steam-jet. 


Heron's  eolipile. 


16 


INTRODUCTION— HISTORICAL 


ress  that  to  the  acute  mind  of  Roger  Bacon  opened  a  vista  of  the 
future  which  he  expressed  in  the  following  prophetic  words: 

"Men  may  construct  for  the  wants  of  navigation  such  machines 
that  the  greatest  vessels,  directed  by  a  single  man,  shall  cut  through 
the  rivers  and  seas  with  more  rapidity  than  if  they  were  propelled  by 
rowers;  chariots  may  be  constructed  which,  without  horses,  shall 
run  with  immeasurable  speed.  Men  may  conceive  machines  which 
could  bear  the  diver,  without  danger,  to  the  depth  of  the  waters. 
Men  could  invent  a  multitude  of  other  engines  and  useful  instru- 
ments, such  as  bridges  that  shall  span  the  broadest  rivers  without 
any  intermediate  support.  Art  has  its  thunders,  more  terrible  than 
those  of  heaven.  A  small  quantity  of  matter  produces  a  horrible 
explosion,  accompanied  by  a  bright  light;  and  this  may  be  repeated 

so  as  to  destroy  a  city  or 
entire  battalions." 


Destruction  of  Denys  Papin's  steam-boat  in  1695, 
by  the  bargemen  of  the  Seine  (by  Figuier). 


Bacon  was  riot  a  man 
to  speak  or  write  in  this 
manner  at  random.  His 
experiments  led  him  to  the 
conclusions  he  has  thus 
recorded,  for  he  was  by 
far  the  most  talented  and 
indefatigable  experimental 
philosopher  of  his  age. 

The  first  application  of 
steam  under  pressure  to 
the  propulsion  of  a  boat 

was  made  by  Blasco  de  Garay  at  Barcelona,  Spain,  in  1543,  although 
a  few  experiments  on  the  power  to  lift  water  by  steam-pressure 
were  made  at  an  earlier  date  and  continued  into  the  seventeenth 
century  by  De  Caus,  Branca,  and  the  Marquis  of  Worcester.  Dr. 
Denys  Papin,  in  1695,  was  probably  the  first  to  use  the  moving 
piston  and  the  walking-beam  on  a  steam-boat  in  the  river  Seine  in 
France.  To  Dr.  Papin  may  be  attributed  the  origin  of  the  steam- 
engine  for  power  use.  Steam  under  high  pressure  was  used  by  him 
in  the  "  Papin  digester,"  a  name  surviving  at  the  present  time. 
Savory,  a  contemporary  of  Papin,  in  England,  built  water-raising 


INTRODUCTION— HISTORICAL 


17 


Newcomen's  pumping-engine. 


engines  by  direct  action  of  steam  and  a  vacuum:  but  little  progress 
was  made  until  Newcomen  brought  out  the  piston  and  walking- 
beam  engine,  for  deep-well 
and  mine  pumping,  in  1705; 
from  which  time  there  was 
but  little  improvement  for  a 
half  century,  until  the  time  of 
James  Watt,  although  Leu- 
pold,  in  1720,  invented  a  two- 
cylinder,  single-acting  piston- 
engine,  moved  by  steam- 
pressure  and  exhausting  into 
the  atmosphere. 

James  Watt  commenced 
experimental  work  on  the 
steam-engine  about  1761, 

making  rapid  progress  in  improvements  of  single-acting  types,  and 
by  closing  the  top  of  the  cylinder  for  the  double-acting  effect.     The 

water-spray  or  separate  con- 
denser and  air-pump,  the  atmos- 
pheric siphon  condenser,  the 
steam-jacketed  cylinder,  the  par- 
allel-motion crank,  the  fly-wheel, 
and  the  fly-ball  governor  were 
invented  or  applied  by  Watt 
previous  to  1782,  at  which  time 
he  received  a  patent  for  the  cut- 
off for  using  steam  expansively 
in  the  cylinder.  Thus  it  seems 
that  the  main  features  of  the 
modern  steam-engine  were  in 
use  at  the  close  of  the  eighteenth 
century. 

Efforts  to  apply  this  pioneer 
Watt's  single-acting  condensing-engine.       of  motive  power  to  boats  were 

made  during  the  early  part  of 

the  eighteenth  century,  and  later  in  the  century  to  vehicles,  with 
a  few  improvements  in  its  action  and  economy. 


18  INTRODUCTION— HISTORICAL 

The  compound  steam-engine  was  patented  in  1781  by  Hornblower, 
in  England,  from  which  time  steam-pressure  as  a  practical  power 
became  progressive. 

During  the  first  century  of  the  usefulness  of  steam  little  or  no 
pressure  was  used  in  its  operation  for  power,  and  not  until  the  close 
of  the  eighteenth  century  was  the  then-called  high-pressure  engine 
brought  into  use,  when  25  pounds  per  square  inch  was  considered 
high  pressure,  and  during  the  first  half  of  the  nineteenth  century 
50  pounds  was  named  as  high  pressure,  although  much  higher  pres- 
sures were  used  for  special  purposes.  In  1840  the  Perkins  steam- 
gun  was  operated  by  the  author  in  New  York  City,  with  a  steam- 
pressure  of  1,000  pounds  per  square  inch.  It  made  wafers  of  bullets 
against  an  iron  target;  but  the  steam-gun  did  not  prove  practicable. 
At  the  dawn  of  the  nineteenth  century  patents  upon  the  principles 
of  the  application  of  high-pressure  steam  to  engines  were  held  by 
Trevethick  and  Vivian,  in  England,  which  were  a  menace  to  progress 
by  contemporaries;  yet  progress  in  design  and  application  to  the 
propulsion  of  boats  and  the  locomotive  began  the  infancy  of  its 
future  career. 

In  the  hands  of  Stevens  and  Fulton  in  the  United  States,  and  of 
Bell,  Dodd,  and  others  in  England,  steam  navigation  made  a  won- 
derful stride  during  the  first  half  of  the  century;  while  the  stationary 
engine  plodded  along  seemingly  in  the  rut  of  the  slide-valve  move- 
ment and  slow  speed.  The  cylindrical  multitubular  boiler  became  the 
leading  type  for  the  economical  generation  of  steam  and,  with  the 
internal  furnace,  the  fixed  type  for  marine  and  locomotive  service. 

The  duty  of  a  motive  power  is  measured  by  the  foot-pounds  work 
produced  per  pound  of  a  given  heat-unit  capacity  of  the  fuel,  or  the 
initiative  value  of  the  power-producer.  The  progress  of  improve- 
ment during  the  first  half  of  the  nineteenth  century  was  registered 
by  the  improvement  in  pumping  service,  which  gradually  advanced 
from  a  duty  of  20,000,000  at  the  beginning  of  the  century,  to  108,- 
000,000  in  1842,  per  bushel  of  94  pounds  Welsh  coal,  or  equivalent 
to  1,148,936  foot-pounds  per  pound  of  coal;  all  due  to  improvements 
in  boiler  and  engine  design,  compounding,  and  more  perfect  condens- 
ing effect. 

During  the  latter  half  of  the  nineteenth  century  the  duty  in  pump- 
ing-engines  of  the  larger  size  had  been  raised  to  above  1,600,000 


INTRODUCTION— HISTORICAL 


19 


foot-pounds  per  pound  of  coal  yielding  10,000  heat-units  from  the 
boiler  in  steam.  This  advance  was  largely  due  to  increased  boiler- 
pressure,  160  to  185  pounds  gauge,  and  triple-expansion  engines,  giv- 
ing efficiencies  of  above  21  per  cent. 

In  this  period  the  relative  proportions  of  cylinder  size  and  stroke 
have  been  changed  to  more  nearly  equalize  the  volume  and  wall  sur- 
face, which  means  short  stroke  and  larger  diameter;  types  of  the  high- 
speed, tandem  compound  engines  of  to-day.  From  the  middle  of  the 
century  on,  improvements  in  valve-gear  continued  to  be  made;  the 
poppet-valve  became  established  for  engines  in  marine  and  river 


Hornblower's  compound  pumping-engine. 

service,  and  steam  and  exhaust  lap  and  lead  became  an  established 
principle  in  engines  of  the  slide-valve  and  other  types. 

The  latter  half  of  the  nineteenth  century  was  a  marked  period  in 
developing  the  efficiency  and  usefulness  of  the  steam-engine. 

Compression  of  the  exhaust  at  the  terminal  of  the  piston-stroke 
became  a  fixed  principle  in  design  for  smooth  running  in  high-speed 
engines,  although  its  efficiency  is  still  a  matter  of  discussion. 

The  quick  and  controllable  valve-movement  came  with  the  Corliss 
type  and  established  an  advanced  efficiency  in  the  development  of 
steam-power,  and  with  increased  steam-pressure,  short  cut-off  and 
compounding  have  brought  the  coal  value  of  a  horse-power  below 
1  pound  per  hour. 


20  INTRODUCTION— HISTORICAL 

The  quadruple-expansion  system  seems  to  have  reached  a  point 
that  bars  further  progress  in  that  direction;  but  with  the  opening 
of  the  twentieth  century  the  long-dormant  rotary  principle  received  a 
new  and  practical  impulse  in  the  successful  instalment  of  the  steam- 
turbine;  although  not  showing  as  yet  an  advance  in  steam  efficiency, 
it  fills  a  long-felt  want  for  compactness  and  speed  for  marine  and 
electric  requirement,  and  thus  has  become  the  means  for  making  a 
great  advance  in  the  usefulness  of  steam-power. 

The  principle  of  Heron's  engine  was  the  utilization  of  the  reaction 
caused  by  the  escape  of  steam  from  jets  protruding  tangentially  from 
a  hollow  globe,  this  reaction  causing  the  rotation  of  the  globe. 

More  than  seventeen  hundred  years  later — in  1629 — Giovanni 
Branca,  an  Italian  inventor,  devised  an  impact  steam-turbine  em- 
bodying the  same  principles  as  the  familiar  impact  water-wheel  of  to- 
day, except  that  a  jet  of  steam  instead  of  water  impinged  upon  the 
vanes  of  the  paddle-wheel  and  caused  it  to  revolve.  The  advent  of 
the  reciprocating  steam-engine  early  in  the  eighteenth  century  di- 
verted attention  from  the  earlier  attempts  to  perfect  a  rotating  engine, 
and  it  was  not  until  near  the  end  of  the  nineteenth  century  that  the 
steam-turbine  again  made  its  appearance  as  a  commercial  possibility. 
De  Laval,  in  Sweden,  in  1883,  and  Parsons,  in  England,  in  1884,  con- 
structed successfully  operating  steam-turbines,  and  a  continuous 
process  of  development  and  improvement  has  demonstrated  the  prac- 
ticability and  commercial  value  of  this  form  of  motor  in  two  distinct 
types,  obtaining  efficiencies  which  rank  with  the  best  reciprocating 
engines.  The  performance  of  the  steam-turbine,  with  the  several 
very  important  advantages,  justifies  the  belief  that  the  field  held 
for  more  than  a  century  by  the  reciprocating  engine  of  Watt  is  likely 
to  be  seriously  invaded  by  this  modern  application  of  the  earliest 
principles  of  steam-engineering,  which  is  made  possible  by  the  better 
materials  and  workmanship  and  the  more  intelligent  skill  now  avail- 
able. 

We  cannot  improve  on  the  expressions  of  Prof.  R.  H.  Thurston 
in  regard  to  the  progress  in  the  realization  of  the  practical  possibilities 
and  economics  from  the  power  of  steam: 

"The  end  of  the  nineteenth  century  is  that  of  one  which  will  always 
remain  preeminent  in  history  as  the  age  in  which  the  steam-engine 


INTRODUCTION— HISTORICAL  21 

took  shape  in  the  hands  of  Watt  and  Sickles  and  Corliss  and  Greene, 
of  Porter,  and  their  successors,  and  thus  brought  in  the  factory 
system  and  all  our  modern  methods  of  production,  in  the  improve- 
ment of  the  condition  of  the  people,  and  in  all  the  material  advance- 
ment in  the  industrial  arts,  which  has  made  the  century  distinctively 
one  of  supremacy  of  the  mechanic  arts.  The  close  of  the  century 
finds  the  steam-engine,  though  threatened  with  displacement  by 
other  motors,  in  the  view  of  many  writers,  nevertheless  the  great 
motor  of  the  age.  Substantially  all  of  the  power  employed  by  the 
civilized  world  is  supplied  by  this  great  invention — congeries  of  in- 
ventions, rather — the  product  of  a  series  of  improvements,  of  an 
evolution  effected  during  the  hundred  years  or  more  just  past.  The 
limit  to  be  possibly  attained  in  its  development  and  perfection  will 
always  remain  a  subject  of  intense  interest  to  the  profession  and  to 
the  world. 

"  Reviewing  the  history  of  the  growth  of  this  form  of  steam- 
engine,  it  will  be  seen  that  its  progress  has  illustrated  that  of  the 
machine  in  all  its  forms,  and  that  the  steam  pumping-engine  gives 
the  engineer  a  record  of  greater  extent  and  of  more  representative 
character,  as  exemplifying  the  evolution  of  the  machine,  than  does 
any  other  type. 

"The  twentieth  century  will  very  probably  see  a  change  in  the 
curve  of  our  lines,  if  not,  in  some  respects,  a  decided  halt  or  a  reversed 
curvature,  and  it  is  perhaps  even  more  probable  that  the  field  of  the 
steam-engine  will  become  greatly  restricted  by  the  introduction  of 
other  heat-motors,  as  well  as  by  the  general  employment  of  electricity 
as  a  medium  of  extensive  power-distribution  from  hydraulic  and 
pneumatic  prime  movers. 

'The  steam-engine  has  now  been  so  far  perfected,  and  the  prac- 
tical limits  of  pressure  are  coming  to  be  so  nearly  approached  by 
steam-boiler  constructors  and  users,  that  but  little  more  can  be  ex- 
pected of  the  designer;  and  even  with  the  costlier  types  of  engine, 
practically  justifiable  with  exceptionally  high  costs  of  fuel,  uninter- 
rupted working,  and  low  values  of  money,  as  in  some  instances  with 
the  steam  pumping-engine,  commercially  practicable  progress  seems 
likely  henceforth  to  prove  very  slow.  These  costly  types  of  engine 
must  necessarily  have  a  comparatively  narrow  field.  With  the  com- 
mon case  of  moderate  cost  of  fuel,  intermittent  duty,  comparatively 


22 


INTRODUCTION— HISTORICAL 


high  value  of  money  in  the  business,  or  absolute  scarcity  with  the  buyer, 
gains  seem  likely  hereafter  to  be  rather  in  the  direction  of  cheapened 
methods  of  construction  and  simplification  of  design." 

The  progress  in  the  economy  of  fuel  by  increased  steam-pressure 
in  marine  service  during  the  past  three-quarters  of  a  century  has 
been  most  marvellous,  and,  together  with  the  improvements  in  con- 
struction of  both  engines  and  boilers,  multiple  expansion  with  sur- 
face condensation,  has  resulted  in  the  saving  of  about  900  per  cent, 

. 01 2MMM Caloric  Engine 


.035i 
.077  i 


Direct  Acting  Pump 
__  Early  Slide  Valve 
—^MMI—^MIM^MHHMK  Automatic  High  Speed 
—^••^MM—M^^^^^MM  Simple  Condensing 

_HM__«nBMM.^_^MMH__^_^B—  •  Steam  Turbine 


.18' 


216" 


Corliss  Condensing 
M  Compound  Condensing 
_T::['!c  Condensing 
^__i  Quadruple 


.30" 


Explosive  Motor 
Diagram  of  progress. 

reducing  the  old-time'  consumption  of  about  10  pounds  to  nearly  1 
pound  of  coal  per  indicated  horse-power.  The  progress  in  the  rise 
of  steam-pressure  and  consumption  of  coal  per  indicated  horse-power, 
with  few  exceptions,  is  shown  approximately  in  the  following  table: 


YEAR. 

Steam-pressure. 

Coal  per  I.  H.  P. 

1830                        

13  t 
18 
24 
40 
50 
75 
125 
160 

o    141 
25 
40 
50 
75 
100 
150 
'  200 

bs.  ga 
i 

uge 

9       to  10     It 
54     "     6 
4       "     5 
3       "     3J 
24     "     3 
21     "     2J 
14     "     2 

if       "        l^T 

)S.    p( 

jr  he 

ur 

1840                 

1850         

I860 

1870 

1880 

1890                            .  .    . 

1900          

INTRODUCTION— HISTORICAL  23 

In  stationary  service  the  steam-pressures  have  been  greater  than 
above  stated  in  the  earlier  years,  and  the  coal-saving  has  been  im- 
proved in  the  most  modern  designs  for  the  greatest  possible  expan- 
sion and  mechanical  efficiency  for  high-power  service.  The  diagram  of 
progress  shows,  in  percentages,  the  approximate  progress  of  thermal 
efficiency  in  different  types  and  designs  of  engines  for  motive  power. 

The  rapid  progress  recently  made  in  steam-turbine  design  has 
given  it  a  leading  position  in  its  special  field  of  usefulness.  Speed 
with  power  is  a  rare  combination  for  useful  effect  in  electrical  gen- 
eration, as  well  as  in  marine  propulsion,  in  which  both  have  made 
new  records  in  their  respective  lines  of  practical  operation. 

We  can  scarcely  realize  the  fact  of  the  startling  changes  in  the 
industrial  and  financial  values  in  all  the  civilized  world  that  have 
occurred  within  our  memory  and  that  have  been  due  to  education 
and  its  bearing  upon  this  inventive  age,  and  in  which  steam,  with  its 
work,  with  been  one  of  the  principal  factors. 


CHAPTER    II 

STEAM   AND   ITS   PROPERTIES 

STEAM,  the  vapor  from  water,  is,  like  water,  the  product  of  a  com- 
bination of  the  so-called  permanent  gases,  hydrogen  and  oxygen, 
in  the  proportion  by  weight  to  one  of  the  former  to  eight  of  the  latter 
gas,  and  by  volume  one  of  hydrogen  to  two  of  oxygen. 

This  combination  of  these  gases  to  form  water,  or  its  vapor,  and 
steam  is  permanent  up  to  a  temperature  to  or  above  2,000°  F.,  when 
dissociation  takes  place  from  heat  alone;  but  at  much  lower  tempera- 
tures when  in  contact  with  ignited  carbon  in  coal  and  other  fuels; 
the  oxygen  combining  with  the  carbon  forming  carbonic  acid,  C02, 
and  carbonic  oxide  gas,  CO,  setting  hydrogen  free,  and  thus  forming 
hydrocarbon  compounds. 

Water  vaporizes  at  temperatures  below  its  freezing-point,  and  as 
ice  its  vapor-pressure  becomes  zero  at  about  — 101°  F.  At  32°  F.  the 
vapor  of  water  exceeds  208,000  volumes  at  as  near  a  vacuum  as 
practically ,  possible,  with  an  increasing  density  to  about  20,000 
volumes  at  1  pound  absolute  pressure  and  temperature  of  102°  F., 
and  to  2,361  volumes  at  10  pounds  absolute  pressure  and  temperature 
of  193°  F.  As  the  temperature  of  the  boiling-point  is  neared  its  den- 
sity increases,  and  under  atmospheric  pressure  (14.7  absolute),  at 
212°  F.  its  vapor  capacity  is  1,646  volumes,  or  26.36  cubic  feet  per 
pound  of  steam,  weighing  .03794  pound  per  cubic  foot. 

Steam  when  blown  into  the  atmosphere  expands  to  atmospheric 
pressure  with  a  temperature  of  212°  F.,  and  has  but  one-half  the  density 
of  the  atmosphere ;  hence  it  rises  quickly,  and,  mixing  with  the  air,  is 
cooled,  and  by  condensation  into  vesicles  becomes  a  cloud.  Pure 
steam  is  perfectly  transparent,  and  so  appears  when  looking  through 
a  jet  close  to  the  nozzle.  The  liberation  of  steam  and  vapor  con- 
tinues below  atmospheric  pressure  in  increasing  volume  per  pound 
of  water  or  vapor  with  a  decreasing  temperature  of  its  boiling-point 
and  absolute  pressure.  This  property  of  evaporation  at  negative 
pressures  and  low  temperatures  has  become  a  most  valuable  adjunct 
24 


STEAM  AND  ITS   PROPERTIES 


25 


of  industrial  work,  indispensable  in  the  modern  methods  of  sugar 
and  salt  manufacture,  and  largely  in  use  in  the  so-called  vacuum- 
drying  of  various  kinds  of  material  and  the  condensation  of  liquids. 

The  following  tables  give  the  volume  of  1  pound  of  water  in 
vapor  at  various  temperatures  and  pressures  from  and  below  the 
boiling-point  of  water  at  atmospheric  pressure,  and  the  elastic  force 
of  vapor  at  various  temperatures. 

TABLE  I. — BOILING  AND  VAPORIZING  TEMPERATURES  OF  WATER,  AT  AND  BELOW 
ATMOSPHERIC  PRESSURE,  WITH  PRESSURES  AND  THE  VOLUME  OF  1  POUND 
OF  VAPOR.  (Claudel.) 


PRESSURE. 

PRESSURE. 

Tempera- 
ture, 
Fahren- 
heit. 

Volume  of 
1  pound, 
cubic  feet. 

Tempera- 
ture, 
Fahren- 
heit. 

Volume  of 
1  pound, 
cubic  feet. 

Mercury, 
inches. 

Per 
square 
inch, 

Mercury, 
inches. 

Per 
square 
inch, 

pounds. 

pounds. 

212° 

29.92 

14.70 

27.2 

120° 

3.43 

1.68             204.9 

210 

28.75 

14.12 

28.2 

115 

2.97 

1.46            234.7 

205 

25.99 

12.77 

31.0 

110 

2.57 

1.27             268.1 

200 

23.46 

11.52 

34.1 

105 

2.23 

1.09            307.7 

195 

21.14 

10.38 

37.6 

100 

1.91 

.94             353.4 

190 

19.00 

9.33 

41.5 

95 

1.64 

.81             408.2 

185 

17.04 

8.37 

45.9 

90 

1.41 

.69             471.7 

180 

15.29 

7.51 

•     50.8 

85 

1.20 

.59             549.5 

175 

13.65 

6.71 

56.4 

80 

1.02 

.50             641.0 

170 

12.18 

5.98 

62.4 

75 

.87 

.43             746.3 

165 

10.84 

5.33 

69.8 

70 

.73 

.36' 

877.2 

160 

9.63 

4.73 

75.0 

65 

.62 

.30 

1031.0 

155 

8.53 

4.19 

87.3 

60 

.51 

.25 

1220.0 

150 

7.55 

3.71 

97.8 

55 

.42 

.21 

1429.0 

145 

6.66 

3.27 

110.0 

50 

.36 

.18 

1695.0 

140 

5.86 

2.88 

124.1 

45 

.30 

.15 

2041.0 

135 

5.17 

2.54 

140.1 

40 

.25 

.12 

2439.0 

130 

4.51 

2.21 

158.7 

35 

.20 

.10 

2941.0 

125 

3.93 

1.93 

180.5 

32 

.18 

.09 

3226.0 

TABLE  II. — ELASTIC  FORCE  OF  VAPOR  OF  WATER  AT  TEMPERATURES  FROM  0  TO 
212°  F.,  AND  ATMOSPHERIC  PRESSURE  OF  14.7  POUNDS.     BAROMETER,  29.92. 


Tempera- 
ture, 
Fahren- 

Elastic 
force, 
inches, 

Tempera- 
ture, 
Fahren- 

Elastic 
force, 
inches, 

Tempera- 
ture, 
Fahren- 

Elastic 
force, 
inches, 

j  Tempera- 
ture, 
Fahren- 

Elastic 
force, 
inches. 

heit. 

mercury. 

heit. 

mercury. 

heit. 

mercury. 

heit. 

mercury. 

0° 

.044 

62° 

.556 

122° 

3.621 

182° 

15.960 

12 

.074 

72 

.785 

132 

4.752 

192 

19.828 

22 

.118 

82 

1.092 

142 

6.165 

202 

24.450 

32 

.181 

92 

1.501 

152 

7.930 

212 

29.921 

42 

.267 

102 

2.036 

162 

10.099 

52 

.388 

112 

2.731 

172 

12.758 

26 


STEAM   AND  ITS   PROPERTIES 


Table  II  will  be  found  convenient  for  aiding  the  formulas  for 
computing  the  evaporation  in  Table  IV  for  other  air  temperatures 
and  humidities  as  stated  in  the  heading  of  that  table. 

TABLE  III. — BOILING-POINT  OF  PURE  WATER  AT  PRESSURES  BELOW  THE  ABSOLUTE 
ATMOSPHERIC  PRESSURE  OF  14.7  POUNDS  PER  SQUARE  INCH. 


Barometer, 
inches. 

Absolute 
gauge- 
pressure, 
pounds. 

Boiling-point, 
Fahrenheit. 

Barometer, 
inches. 

Absolute 
gauge- 
pressure, 
pounds. 

Boiling-point, 
Fahrenheit. 

29.92 

14.70 

212° 

20.25 

9.94 

193° 

29.33 

14.40 

211 

19.82 

9.73 

192 

28.75 

14.11 

210 

19.41 

9.53 

191 

28.18 

13.83 

209 

19.00 

9.33 

190 

27.61 

13.55 

208 

18.59 

9.12 

189 

27.06 

13.28 

207 

18.19 

8.93 

188 

26  .52 

13.02 

206 

17.81 

8.74 

187 

25.99 

12.76 

205 

17.42 

8.55 

186 

25.46 

12.50 

204 

17.05 

8.36 

185 

24.94 

12.23 

203 

16.31 

8.00 

182 

24.44 

12.00 

202 

14.27 

7.00 

174 

23.94 

11.75 

201 

12.23 

6.00 

166 

23.45 

11.51 

200 

10.19 

5.00 

157 

22.97 

11.28 

199 

8.16 

4.00 

147 

22.49 

11.04 

198 

6.09 

3.00 

135 

22.03 

10.81 

197 

4.07 

2.00 

123 

21.57 

10.59 

196 

2.04 

1.00 

109 

21.13 

10.37 

195 

0.00 

0.00 

98.7 

20.68 

10.15 

194 

Pure  water  is  said  to  boil  in  as  near  a  perfect  vacuum  as  its  rising  va- 
por by  its  rapid  expansion  will  allow,  at  a  temperature  of  98°  F.  This 
was  indicated  by  the  double-bulb  vacuum-tube  in  Franklin's  experi- 
ment. The  author  has  seen  a  carafe,  partly  filled  with  water  at  50°  F., 
placed  under  a  nearly  perfect  vacuum  made  by  the  pump  of  a  vacuum 
ice-making  machine ;  the  water  boiled  violently  for  a  few  seconds,  the 
agitation  not  ceasing  until  ice  began  to  form  and  became  solid  in  a  few 
minutes.  .The  violent  agitation  was  caused  by  the  liberation  of  air. 

Water  holding  salts  and  other  substances  in  solution  has  its  boiling 
temperature  raised  above  212°  F.,  and  thus  becomes  a  valuable  means 
of  transmitting  heat  for  boiling  or  concentrating  liquids  at  open-air 
exposures  and  temperatures  slightly  above  the  boiling-point  of  water. 
The  following  are  convenient  solutions  for  limiting  temperatures  in 
double-jacket  kettles: 

Common  salt,  for  any  temperature  up  to  its  point  of  saturation, 
227°  F. 


STEAM  AND  ITS  PROPERTIES 


27 


Carbonate  of  soda,  up  to  220°  F. 

Nitrate  of  potash,  up  to  240°  F. 

Nitrate  of  soda,  up  to  250°  F. 

Carbonate  of  potash,  up  to  275°  F. 

Acetate  of  potash,  up  to  336°  F. 

The  operation  of  chemical  and  industrial  processes  with  heat 
above  the  boiling-point  of  water  is  a  most  important  point  for  ob- 
taining uniform  results  in  the  vast  chemical,  pharmaceutical,  and 
provision-canning  industries  of  this  age.  When  absolute  uniformity 
of  temperature  at  a  few  degrees  above  the  boiling-point  of  water  is 
required,  there  is  no  more  safe  and  reliable  method  than  by  the  use  of 
one  of  the  above-named  salts  in  part,  as  a  bath  or  a  saturated  solution 
in  open  single-jacketed  kettles  heated  by  fire,  or  in  double-jacketed 
kettles  heated  by  steam,  in  which  the  boiling  temperature  of  the 
heat-transmitting  medium  can  always  be  under  observation  with  a 
thermometer.  By  the  direct  heat  of  steam,  as  in  the  usual  method 
of  taking  steam  from  a  high-pressure  factory-boiler,  the  pressure  and 
temperature  are  often  regulated  by  guess,  a  safety-valve,  or  a  regu- 
lator; but  these  have  their  troubles  and  dangers. 
TABLE  IV. — APPROXIMATE  HEAT  REQUIRED  FOR  EVAPORATING  WATER  AT  AND 

BELOW  THE    BOILING-POINT,   FROM  OPEN  VESSELS  IN  CALM  AlR  AT  A  TEMPER- 
ATURE   OF    52°  F.    AND    86    PER    CENT    HUMIDITY.  (Box.) 


Tem- 
perature 
of  water. 

WATER   EVAPO- 
RATED PER  SQUARE 
FOOT    PER   HOUR 
IN    CALM   AIR. 

Time  to 
evapo- 
rate 
1  pound 
of  water 
in  hours. 

Heat 
lost  by 
radia- 
tion 
from 
surface. 
Units 
per  hour. 

Heat 
carried 
off  by 
air. 

Units. 

Latent 
heat  of 
vapor- 
ization. 
Units. 

Total 
heat  to 
evapo- 
rate 
1  pound 
of  water. 
Units. 

Total 
heat  per 
square 
foot  per 
hour. 
Units. 

Cubic 
feet  of 
air  at 
52°  F. 
to  evap- 
orate 1 
pound 
of 
water. 

Pounds. 

Depth  in 
inches. 

62° 

.0143 

.00275 

70.0 

11.3 

888 

1,071 

2,750 

39 

4,807 

72 

.0343 

.0066 

29.2 

23.4 

753 

1,064 

2,500 

86 

2,036 

82 

.0615 

.0118 

16.3 

35.2 

649 

1,057 

2,280 

140 

1,160 

92 

.0986 

.0190 

10.2 

47.0 

555 

1,050 

2,080 

204 

747 

102 

.150 

.0288 

6.67 

62.7 

449 

1,043 

1,910 

287 

486 

112 

.221 

.0425 

4.52 

76.7 

387 

1,036 

1,770 

392 

350 

122 

.315 

.0606 

3.13 

91.2 

326 

1,029 

1,640 

524 

253 

132 

.454 

.0873 

2.20 

106.8 

278 

1,022 

,535 

698 

184 

142 

.634 

.122 

1.58 

122.5 

241 

1,015 

,450 

918 

146 

152 

.871 

.168 

1.15 

141.1 

206 

1,008 

,376 

1,197 

112 

162 

1.18 

.227 

.848 

156.4 

193 

1,000 

,326 

1,564 

95 

172 

1.57 

.302 

.637 

175.5 

179 

993* 

,284 

2,016 

81 

182 

2.06 

.396 

.485 

193.2 

168 

986 

,248 

2,573 

70 

192 

2.66 

.512 

.374 

215.7 

164 

979 

,224 

3,268 

64 

202 

3.41 

.656 

.293 

237.7 

161 

972 

,203 

4,106 

58 

212 

4.32 

.831 

.232 

257.0 

160 

966 

1,186 

5,112 

54 

28 


STEAM   AND  ITS  PROPERTIES 


The  above  table  was  derived  from  Regnault's  experiments  and 
verified  by  Box  practically  as  to  quantity,  depth,  and  time.  The 
formula  for  evaporation  is  (1)  E  =  (243  +  (3.7 X t)  X(V-v),  in  which 
E  =  evaporation  per  square  foot  per  hour  in  grains;  t  =  temperature 
of  the  water;  V  =  elastic  force  of  vapor  at  temperature  t;  v  =  force  of 
vapor  in  air  due  to  its  percentage  of  humidity;  or,  by  the  table,  II. 
V  =  .388  for  52°  and  v  =  .388  X  .86  =  .334.  For  example,  for  water  62°; 
air  52°,  and  humidity  .86, 
(1)  E  =  (243  +  (3.7  X 62)  X  (.556  - 334}  =  472.4  X  .222  - 104.8  grains,  and 

.    =.0149  pound  theoretical  evaporation  per  hour. 

/  *vJL/w 

The  second  and  third  columns  in  the  table  represent  the  experi- 
mental values. 

The  employment  of  a  vacuum  in  boiling  and  evaporating 
water  in  the  art  of  food  preparation  has  become  an  important 
item  in  the  industrial  economy  of  these 
times.  Among  the  many  devices  of  the 
vacuum  system  of  evaporation  we  il- 
lustrate the  principles  of  its  operation 
in  an  apparatus  (shown  in  Fig.  9)  for 
obtaining  fresh  water  from  salt  water 


FIG.  9. — Fresh-water  still. 


FIG.  10. — Vacuum  salt-pan. 


by  the  use  of  steam  as  the  heating  medium,  which  represents  a 
fresh-water  still : 


STEAM  AND  ITS  PROPERTIES 


29 


The  chamber  is  kept  supplied  half  full  of  salt  water  and  kept  be- 
low saturation  by  blowing  off.  The  vapor  is  drawn  off  through  the 
perforated  pipe  at  the  top  through  a  condenser  by  the  vacuum-pump. 


FIG.  11. — Elevation  of  a  sugar-pan. 

The  boiling  temperature  of  the  salt  water  of  the  ocean  is  about 
153°  F.,  with  a  26-inch  vacuum.  The  condensed  steam  from  the  coils 
is  saved  and  fed  to  the  boilers.  The  condensed  vapor  from  the  salt 


30  STEAM  AND  ITS  PROPERTIES 

water  is  aerated  and  cooled  for  drinking.  For  the  distillation  of 
water  for  ice-making  this  principle  seems  to  be  the  most  economical 
conserver  of  heat  known.  By  devices  of  double  and  triple  effect, 
with  coal  at  New  York  prices,  pure  distilled  water  can  be  produced 
at  a  cost  of  about  75  cents  a  thousand  gallons;  and  when  using  the 
exhaust  steam  from  a  power-plant,  the  cost  of  producing  a  limited 
amount  of  distilled  and  aerated  water  is  a  mere  nominal  item. 

The  manufacture  of  salt  by  the  vacuum  process  is  becoming  an 
important  item  in  this  industry.  In  Fig.  10  is  shown  the  initial 
evaporating  section  of  a  triple-effect  system  consisting  of  three  evap- 
orating-pans  set  side  by  side  with  their  terminal  connected  with  the 
condenser  and  air-pump. 

In  this  salt-making  apparatus  A  is  the  vapor  section,  B  the 
heating  section,  consisting  of  a  series  of  vertical  tubes  connected 
from  the  boiler  or  the  exhaust  from  an  engine  by  the  pipe  E.  In  a 
triple-effect  system  the  vapor-chamber  A  is  connected  with  the 
heating  section  B  of  the  next  effect,  and  so  on  to  the  third  effect, 
which  has  its  chamber  connected  to  the  condenser  and  air-pump.  G 
is  the  brine-inlet  and  C  the  crystallizing-chamber,  from  which  the 
crystallized  salt  is  discharged  into  the  settling-chamber  D  through  a 
slide-valve  or  gate.  This  is  a  continuous  system  and  needs  no  sus- 
pension of  the  evaporating  effect  in  each  of  the  three  sections  as  a 
triple  effect. 

In  Fig.  11  is  shown  the  elevation  of  one  section  of  a  sugar-boiling 
plant,  operated  on  the  dry  system  of  evaporation,  in  which  the  vapor 
enters  a  jet-condenser  and  the  condensed  steam  and  water  pass 
down  a  stand-pipe  or  siphon  by  gravity  to  a  cistern  35  feet  below  the 
condenser,  which  seals  the  exit-pipe  against  atmospheric  pressure. 
The  air-pumps  are  only  required  to  keep  the  system  relieved  of  air 
and  uncondensed  vapor. 

In  this  type  of  evaporator  a  series  of  copper  coils  enters  the  evap- 
orating-pan  from  a  header,  and,  circling  around  the  inside,  gives 
sufficient  surface  for  the  work  of  evaporation.  Sometimes  a  surface 
condenser  is  used  with  a  second  pump  for  discharging  the  water  of 
condensation. 


CHAPTER    III 

GENERATION    OF    STEAM 
FURNACES     AND     THEIR     ADJUNCTS 

THE  economical  generation  of  steam  is  becoming  one  of  the  most 
essential  features  in  the  world  of  engineering  design  for  the  produc- 
tion of  power.  The  vast  progress  in  manufacturing  and  producing 
industries  of  this  age  and  their  competitive  relations  not  only  require 
the  utmost  economy  in  the  production  of  power,  but  even  the  fuel 
for  power  has  its  limit  of  production  and  its  liability  to  increased 
cost;  this  serves  as  a  warning  to  harbor  our  resources  of  the  present 
for  future  emergencies. 

The  generator  of  steam  and  its  power-developing  agent,  the 
steam-engine,  have  had  a  slow  growth  in  development  during  the 
progressing  ages  of  civilization,  and  only  during  the  past  century  of 
scientific  research  have  the  principles  for  the  economical  application 
of  this  vast  power  been  mathematically  realized  and  applied. 

The  greatest  economy  in  the  production  of  steam  begins  at 
the  furnace-door — the  method  of  firing  by  which  the  most  perfect 
combustion  is  produced  and  every  atom  of  heat-producing  fuel 
is  consumed  for  the  evolution  of  the  highest  temperature  in  the 
furnace. 

Of  the  fuels  in  use  for  generating  steam,  anthracite  and  bitu- 
minous coal  stand  at  the  head,  in  accordance  with  their  respective 
qualities  in  the  carbon  element.  Wood,  saw-mill  refuse,  lignite,  peat, 
planing-mill  shavings,  bagasse,  tan-bark,  are  in  use  with  appropriate 
furnaces;  while  crude  petroleum  is  gaining  a  leading  fuel  value  in 
districts  where  it  is  cheaper  than  coal  and  in  countries  having  small 
coal  resources.  The  anthracite  coals  vary  from  83  to  90  per  cent  in 
fixed  carbon,  with  the  volatile  matter  generally  varying  inversely 
to  the  fixed  carbon,  so  that  the  total  combustible  averages  about  90 
per  cent.  With  bituminous  coals  the  volatile  element  is  very  large, 

31 


32      GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 

and  with  this  perfectly  consumed,  its  steam-making  value  is  fully 
equal  to  anthracite  per  pound  of  combustible. 

The  steaming  value  of  anthracite  coal  varies  somewhat  with  its 
size  for  a  given  weight,  as  the  ash  products  in  merchantable  coals 
vary  from  about  5J  per  cent  in  broken  and  egg  size  to  above  16  per 
cent  in  pea  and  buckwheat  sizes;  yet  with  properly  designed  grates  for 
burning  the  small  sizes  they  are  the  most  economical  steam-makers 
from  their  low  price. 

Wood  for  steam-making  is  but  little  used,  and  is  mostly  derived 
from  the  waste  in  lumber-making,  such  as  slabs,  sawdust,  mill- 
shavings,  etc.  Cord-wood,  such  as  used  for  steam-making,  contains 
about  55  per  cent  of  its  weight  in  combustible,  combined  with  about 
40  per  cent  of  oxygen,  which  adds  nothing  to  its  heat-producing 
value,  and  only  makes  the  wood  highly  inflammable.  An  average 
of  2J  pounds  of  dry  wood  is  equal  to  1  pound  of  good  anthracite 
or  bituminous  coal.  In  the  following  table  are  given  the  average 
weight  of  air-dried  cord-wood  per  cord  and  its  equivalent  weight  in 
anthracite  or  bituminous  coal: 


TABLE  V. — AVERAGE  WEIGHT  OF  AIR-DRIED  CORD-WOOD  AND  ITS  EQUIVALENT 

WEIGHT  IN  COAL. 


KIND. 

Pounds  per  cord. 

Pounds  of  coal. 

Shell-bark  hickorv 

4470 

1  987 

White  oak  .    . 

3,821 

1  700 

Red-heart  hickory   

3,705 

1  646 

Beach,  red  and  black  oak  
Southern  pine  (pitch-pine)  
Maple 

3,250 
3,375 

2878 

1,444 
1,500 
1  279 

Virginia  pine 

2  690 

1  151 

Spruce  and  New  Jersey  pine 

2  137 

949 

White  and  yellow  pine,  hemlock 

1,900 

844 

Lignite,  or  brown  coal,  is  of  recent  geological  formation.  When 
dry  it  ignites  easily  and  burns  freely,  and  as  a  steam-producing  fuel 
is  between  wood  and  coal  as  to  bulk.  Its  specific  gravity  is  from  1.10 
to  1.25.  It  is  used  in  many  localities  where  it  can  be  obtained  at  a 
less  cost  per  combustible  weight  than  coal  or  wood. 

Peat  or  turf  is  of  little  value  for  steam-making.  In  a  few  locali- 
ties, and  in  Germany,  it  is  briquetted  by  drying  and  compressing,  in 
which  form  it  has  been  in  use  for  some  time,  burning  much  like  wood. 


GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS     33 

Coke  is  but  little  used  for  steam-making;  it  has  a  higher  carbon 
value  per  pound  than  coal  and  makes  a  hot,  clear  fire. 

Sawdust  and  shavings  are  used  in  wood-working  mills  for  steam- 
fuel,  more  for  the  economy  of  disposing  of  them  than  for  their  steam- 
making  value. 

Bagasse  and  straw  in  the  sugar  and  agricultural  districts  are 
used  for  steam-making  as  a  means  of  disposing  of  by-products,  and 
with  bagasse  fired  in  special  furnaces  under  the  long  cylinder  boilers 
set  for  this  purpose,  it  seems  to  be  a  measure  of  real  economy  in  turning 
the  immense  by-product  of  a  sugar  plantation  to  the  best  account. 

The  use  of  petroleum  for  steam-making  has  made  a  vast  stride 
in  late  years,  and  especially  in  and  near  the  oil  districts,  where  its 
price  competes  with  that  of  coal. 

The  oil  constituents  vary  somewhat  in  different  localities,  with  an 
average  of  carbon  .86,  hydrogen  .13,  oxygen  .01,  with  their  specific 
gravity  varying  from  .80  to  .94  and  weighing  from  6.6  to  7.6  pounds 
per  gallon.  The  total  heat  of  combustion  varies  from  19,000  to 
22,000  heat-units  per  pound,  with  a  theoretical  evaporative  power 
of  from  19.6  to  22.7  pounds  of  water  per  pound  of  oil. 

From  comparison  of  the  constituents  of  coal  and  petroleum  the 
heating  value  of  the  oil  is  about  1}  times  that  of  the  coal;  but  in 
practice  the  heating  value  of  oil  has  been  found  to  be  equal  to  twice 
the  value  of  coal  per  pound  in  evaporating  power.  This  has  been 
accounted  for  by  the  more  complete  combustion  of  the  liquid  fuel 
and  freedom  of  the  tubes  from  soot  and  ashes.  The  admission  of 
air  being  under  complete  control  with  the  fine  atomizing  of  the  oil, 
brings  the  air  and  fuel  into  immediate  and  perfect  contact  with  but  a 
very  small  excess  of  air;  while  with  coal  much  of  the  loss  by  com- 
bustion is  due  to  excess  of  air.  Another  point  in  favor  of  oil  fuel  is  the 
saving  in  banked  fires  and  the  convenience  of  instantaneous  starting 
and  extinguishing  the  furnace  fire;  while,  with  a  well-constructed 
furnace  and  boiler-setting,  the  boiler  will  retain  sufficient  heat  during 
the  night  for  a  quick  morning  start. 

Natural  gas,  which  is  largely  in  use  in  the  gas  districts,  with  a 
heating  capacity  of  from  900  to  1,200  thermal  units  per  cubic  foot, 
is  a  matter  for  economical  consideration  as  to  its  cost  per  1,000 
cubic  feet. 


34      GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 

Mr.  J.  M.  Whitham,  who  has  investigated  the  natural-gas  question, 
has  summarized  the  subject  in  the  following  brief  paragraphs: 

1.  In  regard  to  burners,  there  is  but  little  advantage  possessed 
by  one  burner  over  another. 

2.  As  good  economy  is  made  with  a  blue  as  with  a  white  or  straw 
flame,  and  no  better. 

3.  Greater  capacity  may  be  made  with  a  straw-white  than  with  a 
blue  flame. 

4.  An  efficiency  as  high  as  from  72  to  75  per  cent  in  the  use  of 
gas  is  seldom  obtained  under  the  most  expert  conditions. 

5.  The  "air  for  dilution"  is  greater  with  gas  than  with  coal,  so 
that  possible  coal  efficiencies  are  impossible  with  gas. 

6.  Don't  expect,  in  good  commercial  practice,  to  get  a  boiler  horse- 
power on  less  than  from  43  to  45  cubic  feet  of  natural  gas,  the  same 
being  referred  to  60°  F.  and  4-ounce  pressure  above  a  barometer  of 
29.92  inches. 

7.  Fuel  costs  are  the  same  under  best  conditions  with  natural  gas 
at  10  cents  per  1,000  cubic  feet  and  semibituminous  coal  at  $2.87 
per  2,240  pounds.     This  is  based  on  3.5  pounds  of  wet  coal  being 
used  per  boiler  horse-power  per  hour,  or  45  cubic  feet  of  natural  gas. 

8.  Expressed  otherwise,  a  long  ton  of  semibituminous  coal  is  the 
equivalent  of  28,700  cubic  feet  of  natural  gas;  while  a  short  ton  of 
such  coal  is  the  commercial  equivalent  of  25,625  cubic  feet. 

9.  As  compared  with  hand-firing  with  coal  in  a  plant  of  1,500 
boiler  horse-power  output,  coal  being  $2  per  2,240  pounds — consider- 
ing labor-saving  by  the  use  of  gas — natural  gas  should  sell  for  about 
10  cents  per  1,000  cubic  feet. 

The  largest  constituent  of  natural  gas  is  marsh-gas,  CH4,  varying 
from  96  to  67  per  cent;  the  next  is  hydrogen,  H,  varying  from  22  to 
6  per  cent;  the  balance  being  ethane,  C2H4,  from  18  to  5  per  cent, 
with  traces  of  CO  and  C02  and  free  oxygen  and  nitrogen. 

The  economy  of  combustion  in  a  boiler  furnace  is  so  much  a 
matter  of  experience  in  the  management  of  the  fire  and  the  relative 
volume  of  air  allowed  to  pass  through  the  furnace  that  is  not  required 
for  combustion,  and  so  much  depends  upon  good  practice  derived 
from  experience  and  good  judgment  in  the  handling  of  a  fire,  there 
is  but  little  of  value  to  be  said  in  regard  to  its  details. 


GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS    35 

In  the  disposition  of  the  fuel  elements  by  combustion,  1  pound  of 
carbon  requires  2.66  pounds  of  oxygen  or  12  pounds  of  air  or  162  cubic 
feet  at  boiler-room  temperature  for  complete  combustion,  and  having 
a  heat  value  of  14,600  thermal  units. 

One  pound  of  hydrogen  requires  8  pounds  of  oxygen,  36J  pounds 
of  air,  490  cubic  feet,  for  complete  combustion,  with  a  heating  value 
of  62,000  thermal  units.  Thus,  for  example,  for  anthracite  coal  with 
carbon  .91,  hydrogen  .028  per  cent— 162  X  .91  =  147^  cubic  feet  of  air 
for  the  carbon,  and  490  X  .028  =  13|  cubic  feet  of  air  for  the  hydrogen, 
or  161  cubic  feet  of  air  per  pound  of  coal  for  perfect  combustion. 

In  practice  perfect  combustion  cannot  be  obtained  with  less  than 
from  1J  to  2  times  the  quantity  of  air  actually  needed  for  perfect 
combustion. 

The  necessities  for  feeding  the  fire  with  open  doors,  and  the  faulty 
practice  of  letting  too  much  air  into  the  furnace  for  the  consumption 
of  the  gaseous  distillates  above  the  fire,  and  for  smoke  consumption 
of  bituminous  fires,  are  serious  drawbacks  to  the  ultimate  heat  pro- 
duction of  the  furnace. 

The  volume  of  gases  passing  to  the  chimney  is  largely  increased 
by  excess  of  air  to  the  furnace  above  the  actual  requirement  for  com- 
bustion, which  for  each  pound  of  carbon  in  the  coal  and  50  per  cent 
excess  of  air  the  products  of  combustion  will  increase  in  volume 
nearly  in  proportion  to  the  excess  of  air,  or  to  18  pounds  of  air;  and 
as  the  gases  are  expanded  to  nearly  double  their  initial  volume  at  the 
chimney  temperature  of  500°,  it  indicates  a  chimney  volume  of  about 
500  cubic  feet  of  gases  for  each  pound  of  carbon  consumed  in  the 
furnace.  Assuming  that  there  is  no  air  passing  up  the  chimney  other 
than  that  which  has  passed  through  the  fire,  the  higher  the  tempera- 
ture of  the  fire  and  the  lower  that  of  the  escaping  gases  the  better 
the  economy,  for  the  losses  by  the  chimney  gases  will  bear  the  same 
proportion  to  the  heat  generated  by  combustion  as  the  temperature 
of  those  gases  bears  to  the  temperature  of  the  fire.  Then,  if  the  tem- 
perature of  the  fire  is  2,500°,  and  that  of  the  chimney  gases  500°  above 
that  of  the  atmosphere,  the  loss  by  the  chimney  will  be  //<&  =2°  Per 
cent.  As  the  temperature  of  the  escaping  gases  cannot  be  brought 
down  to  that  of  the  boiler,  which  is  fixed,  the  temperature  of  the  fire 
must  be  high  in  order  to  secure  good  economy. 


36    GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 


FIG.  12. — Tupper  model. 


B 'OILER-FURNACES,     GRATE-BARS,     AND 
MECHANICAL     STOKERS 

The  boiler-furnace,  its  type  and  special  design  of  firing  appliances, 
are  matters  of  no  small  moment  in  their  contribution  to  the  economy 

of  steam-generation.  Of  the  num- 
erous models  of  shaking  and  tipping 
grates  on  the  market,  we  can  only 
illustrate  examples  of  a  few  leading 
types. 

The  grate-bars  in  the  Tupper 
furnace  are  in  two  sections  so  that 
one-half  of  the  fire  can  be  dressed 
at  a  time.  The  bars  are  placed  crosswise  and  rock  on  trunnions 
by  a  hand-lever  and  connecting-bar.  The  diagonal  spaces  in  the 
bars  are  made  for  any 
size  coal  required. 

The  McClave  grate 
is  made  in  fore  and 
aft  sections,  so  that 
by  separate  connec- 
tions the  front  or  rear 
section  maybe  shaken 
or  tipped  for  dump- 
ing the  fire.  Each  bar 
forms  a  toothed  comb 
with  a  bell-crank  or 


FIG.  13. — McClave  shaking  grate. 


stub-lever  and  connecting-rod,  pivoted  to  all    the  bars  in  the  sec- 
tion.     When  the  bars  are  closed  the  whole  grate  is  a  continuous 

surface   upon   which   a   slicing-bar   may 
be  used. 

Fig.  14  shows  a  shaking  and  dumping 
grate    composed   of   toothed  sectors  set 
astride  pivoted  crossbars  with  lever  ex- 
^  ^y — \  Vr^^*=J^>  _       tensions,  connected  to  transverse  bars,  so 


FIG.  14. — Sector  grate-bar. 


divided  that  the  grate  may  be  shaken  in 
two  or  three  sections.     Heavy  side-bars 


GENERATION  OF  STEAM-FURNACES  AND  THEIR  ADJUNCTS    37 

carry  the  pivoted  crossbars.     The  individual  sectors  can  be  readily 
removed  when  burned  out  and  new  ones  inserted  at  trifling  expense. 

MECHANICAL     STOKERS 

The  Roney  mechanical  stoker  consists  of  a  hopper  for  receiving 
the  coal,  a  set  of  rocking,  stepped  grate-bars,  inclined  at  an  angle  of 
37°  from  the  horizontal,  and  a  dumping  grate  at  the  bottom  of  the 


FIG.  15. — Roney  mechanical  stoker. 

incline  for  receiving  and  discharging  the  ash  and  clinker.  The 
dumping  grate  is  divided  into  several  parts  for  convenience  in  handling. 
The  coal  is  fed  onto  the  inclined  grate  from  the  hopper  by  a 
reciprocating  pusher,  which  is  actuated  by  an  agitator.  The  grate- 
bars  rock  through  an  arc  of  30°,  assuming  alternately  the  stepped 
and  the  inclined  position.  The  grate-bars  receive  their  motion  from 
a  rocker-bar  and  connecting-rod,  and  these,  with  the  pusher,  are 
actuated  by  the  agitator,  which  receives  its  motion  through  an 
eccentric  from  a  shaft  attached  to  the  stoker-front,  under  the  hop- 
per. The  range  of  motion  of  the  pusher  is  regulated  by  the  feed-wheel 
from  no  stroke  to  full  stroke,  and  the  amount  of  coal  pushed  into  the 
furnace  is  adjusted  according  to  the  demand  for  steam.  The  motion 
of  the  grate-bars  is  similarly  regulated  and  controlled  by  the  position 


38     GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 


of  the  lock-nuts  on  the  connecting-rod.  Each  grate-bar  is  composed 
of  two  parts:  A  vertical  web  provided  with  trunnions  at  each  end, 
which  rests  in  seats  in  the  side-bearers;  and  a  fuel-plate,  ribbed  on  its 


FIG.  16. — Acme  stoker. 

under  side,  which  bolts  to  the  web.  These  fuel-plates  carry  the  bed 
of  burning  coal,  and,  being  wearing  parts,  are  made  detachable,  thus 
reducing  the  cost  of  repairs  to  the  minimum.  The  webs  are  perforated 
with  longitudinal  slots,  so  placed  that  the  condition  of  the  fire  can  be 

seen  at  all  times  without  opening  the 
doors,  and  free  access  had  to  all 
parts  of  the  grate  to  assist,  when 
necessary,  the  removal  of  the  clinker. 
These  slots  also  serve  an  important 
purpose  in  furnishing  an  abundant 
supply  of  air  for  combustion. 


FIG.  17. — Soft-coal  stoker. 


The  Columbian  stoker  is  a  special 
design  for  soft  coal,  which  falls  from 
the  hopper  into  an  upward  inclined  chute,  and  is  pushed  by  a 
plunger  onto  a  coking-plate  and  fixed  small  grate  with  an  independent 


UNIVERSITY 

^X 

W  STEAM— FURNACES  AND  THEIR  ADJUNCTS    39 

air-feed  chamber  for  regulating  the  coking.  The  pushing  of  the 
fresh  coal  against  and  under  the  coking-bank  causes  the  coked  coal 
to  slide  down  the  inclined  grate.  A  supplementary  rocking  grate  at 
the  rear  discharges  the  refuse.  The  air-feed  to  the  small  chamber 
at  the  top  of  the  grate  may  be  under  pressure  from  a  blower,  and, 
thus  mixing  air  with  the  smoke  or  distillates  of  the  fresh  coal,  com- 
pletes its  combustion  in  the  hot  part  of  the  furnace. 

The  travelling  chain-grates  are  receiving  much  attention,  and  we 
illustrate  the  principles  of  several  designs  in  this  type  of  grate  for 
soft  coal. 

In  the  Playford  model  a  multilink-grate  moved  by  a  sprocket- 
shaft  carries  the  coal,  fed  from  a  hopper,  forward  under  the  boiler; 
the  grate  returning  over  a  drum  at 
the  bridge- wall.     A  screw-conveyer 
brings  the  ash  and  clinker  forward 
to  the  pit. 

At  the  front  of  the  furnace,  im- 
mediately above  the  coking  end  of 
the  grate-surface,  is  a  fire-brick  arch 
made  of  common  sized  fire-brick. 
The  arch  becomes  highly  heated,  FIG.  18.— Playford  stoker, 

thus  making  the  front  end  of  the 

furnace  a  reverberatory  chamber  in  which  the  gases  are  liberated 
from  the  coking  fuel  by  distillation.  The  coked  fuel  in  process  of 
combustion  is  carried  by  the  grate  toward  the  rear  of  the  furnace,  while 
the  ash  and  refuse  are  dumped  automatically  under  the  flat  arch  at 
the  bridge-wall.  Forming  the  top  of  that  which  otherwise  would 
be  an  ordinary  bridge-wall  is  a  straight  arch,  overhanging  the  rear 
end  of  the  grate-surface. 

The  Green  travelling  link-grate,  which  we  illustrate  in  Fig.  19,  is 
made  up  of  long  thin  links  of  considerable  depth  and  a  large  and 
uniform  air-space  around  each  link  has  been  provided.  The  longer 
links  afford  an  increased  overhang,  so  as  to  shear  any  clinker  which, 
during  the  travel  of  the  grate,  may  be  brought  up  to  the  bridge-wall, 
while  at  the  same  time  it  completely  clears  the  ash  from  all  the  air- 
spaces of  the  chain  at  every  turn  around  the  rear  sprockets.  The 
links  of  the  chain  are  connected  together  by  bars  of  oval  section, 


40    GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 

which  pass  through  round  holes  in  the  links  or  clips.  The  clips  are 
engaged  by  the  bars,  and  they  in  turn  are  locked  and  held  in  correct 
position  by  binding  links  at  each  end.  The  holes  in  the  clips  have 
a  slot  extending  to  the  bottom  edge,  permitting  any  link  or  clip  to 
be  removed  and  replaced  by  another  one  without  breaking  the  chain, 
removing  the  bars,  or  interfering  with  the  service. 

The  chain  is  supported  at  frequent  intervals  by  rolls  extending 
under  the  entire  width. 

The  framework  is  well  braced  and  stiffened,  to  meet  the  require- 
ments of  hard  service.  In  stokers  exceeding  1\  feet  in  width  there  is 


FIG.  19. — Green  travelling  link-grate. 

provided  an  additional  girder  in  the  centre  for  the  support  of  the  upper 
roll-shafts. 

The  driving  mechanism  consists  of  an  eccentric  with  a  rod  and 
lever,  communicating  motion  by  a  ratchet  and  pawls  to  a  train  of 
gearing.  This  arrangement  permits  quick  adjustment  of  speed  of 
travel  within  a  wide  range.  The  gearing  rests  in  a  strongly  braced 
frame.  Steel  pinions  and  gears  are  used  throughout.  The  eccentric- 
connections  from  the  shaft,  placed  either  above  or  below,  are  made 
through  a  long  relief-spring,  thus  preventing  undue  strain  upon  the 
gear-train  or  the  chain  in  case  of  accident  or  stoppage. 

A  single  large  grate  completely  filling  the  entire  furnace  width  is 
desirable,  and  more  effective  than  two  small  grates  occupying  the 
same  space.  The  flat  coking-breast  or  ignition-arch  combined  with 
a  chain-grate,  as  previously  described,  permits  the  successful  use  of 


GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS    41 


grates  of  any  required  width,  and  also  obviates  the  further  necessity 
of  limiting  the  size  of  boiler-units  because  of  inability  to  provide 
adequate  grate-area. 

In  the  American  stoker  the  coal  is  carried  under  the  grate  from 
the  hopper  by  a  spiral  screw  and  forced  up  over  the  grate.  The 
screw  -  conveyer  or  worm 
(shown  in  the  cut)  is  located 
in  a  trough  that  extends  un- 
der the  magazine,  beneath 
which  is  the  air-box  under 
pressure  from  a  blower. 

In  operation  the  coal  is 
fed  into  the  hopper,  and  is 
carried  by  the  conveyer  into  the  magazine,  which  it  fills,  and,  over- 
flowing on  both  sides,  spreads  upon  the  sides  of  the  grate.  The  coal 
is  fed  slowly  and  continuously,  and,  approaching  the  fire  in  its  upward 


Side  View  of  Stoker. 


End  View. 

FIG.  20. — American  stoker. 


FIG.  21. — American  stoker  under  a  Worthington  water-tube  boiler. 

course,  it  is  slowly  roasted  and  coked,  and  the  gases  released  from  it 
are  taken  up  by  the  fresh  air  entering  through  the  tuyeres,  which 


42    GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 


ignites  them,  and  the  coal  is  then  delivered  as  coke  on  the  grate 
above.  The  continuous  feeding  gives  a  breathing  motion  to  this  coke- 
bed,  thus  keeping  it  open  and  free  for  the  circulation  of  air. 

Every  pound  of  coal  fed  into  the  hoppers  passes  through  the  gas- 
making  process.  The  non-combustible  matter  is  taken  from  the 
furnace  in  the  shape  of  the  usual  ash.  There  is  practically  no  soot. 
With  these  results  it  is  obvious  that  the  combustion  must  be  extraor- 
dinarily good,  resulting  in  a  practically  smokeless  stack. 

The  finest  of  slack  coal  and  also  lump  coal  can  be  used,  as  any 
lump  that  can  be  fed  into  the  hoppers  will  be  crushed  by  the  conveyer, 
there  being  provided  a  set  of  teeth,  placed  at  the  mouth  of  the  con- 
veyer, against  which  the  coal  is  squeezed  and  broken. 

The  end-thrust  of  the  conveyer  is  taken  by  a  frictionless  ball- 
bearing. 

The  conveyer-shaft  is  a  2|-inch  steel  shaft,  on  which  are  strung 
what  are  called  "flights."  These  " flights/'  by  their  reduced  diameters, 
distribute  the  coal  equally  over  the  entire  width  and  length  of  the 
furnace.  The  entire  mass  of  coke  above  the  tuyere-blocks  and  over 
the  side-grate  is  ignited.  The  air  enters  the  stoker  from  front  or 
rear  beneath  the  hopper,  and  discharges  through  the  tuyere-openings. 
The  discharge  of  air  into  each  stoker  is  regulated  by  a  wind-gate 

located  at  the  mouth 
of  the  wind-chamber. 
Air  is  supplied  to 
the  ash-pit  by  supple- 
mentary pipes  from 
the  main  air-trunk. 

The  Jones  stoker 
consists  of  a  plunger 
which  may  be  oper- 
ated directly  by  a 

steam-piston,  and  which  pushes  a  charge  of  coal,  falling  from  the 
hopper  onto  the  fore-plate  of  the  grate,  where  it  is  coked,  the  smoke 
and  gases  being  drawn  into  the  hot  fire  and  burned.  These  stokers 
are  well  adapted  to  other  than  boiler-furnaces  and  operated  by  levers 
in  place  of  the  steam-cylinders. 


FIG.  22. — Jones  stoker. 


GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS    43 


LIQUID      FUEL 

Of  all  forms  of  liquid  fuel  crude  petroleum  has  become  the  standard 
for  economy,  and  its  increasing  production  has  so  decreased  its  cost 
for  fuel  that  in  many  parts  of  this  country  and  in  other  countries  it  is 
cheaper  than  other  fuels. 

The  methods  of  its  economical  use  have  been  so  improved  by 
trials  and  experience  derived  from  the  various  detailed  tests  of  the 
past  few  years,  that  its  best  results  are  now  realized  in  very  exact 
designs  of  furnace-construction. 

Some  of  the  advantages  in  the  use  of  petroleum  for  steam-making 
are  that  its  heating  power  is  greater  per  pound  than  that  of  any  solid 
fuel;  that  it  permits  of  continuous  firing  in  a  closed  furnace,  free  from 
draughts  of  cold  air;  that  its  combustion  is  complete,  with  no  loss  of 
heat  by  ashes,  smoke,  or  soot;  and  that  the  quantity  of  heat  required 
to  maintain  a  constant  pressure  of  steam  may  be  controlled  by  the 
simple  adjustment  of  a  valve  in  the  oil-supply  pipe.  The  boiler- tubes 
are  always  clean  and  in  the  best  condition  for  the  transmission  of  heat 
to  the  water;  starting  and  discontinuing  of  the  fire  are  but  the  work 
of  a  moment,  and  all  cleaning  of  ashes  and  debris  avoided.  The  ad- 
mission of  air  being  under  complete  control,  and  the  fuel  being  burned 
in  atomized  particles  in  contact  with  the  air,  only  a  small  excess  of  air 
above  that  actually  necessary  for  the  complete  combustion  of  the  fuel 
being  required;  all  these  are  points  of  economy. 

The  relative  commercial  value  of  coal  and  petroleum  for  steaming- 
fuel,  apart  from  their  convenience  in  operating  a  steam-plant,  may  be 
summed  up  in  their  relative  heat-unit  values.  A  net  ton  of  coal  is 
credited  with  29,000,000  heat-units;  a  barrel  of  oil  of  42  gallons, 
weighing  6.8  pounds  per  gallon,  at  19,000  heat-units  per  pound,  foots 
up  to  5,426,400  heat-units,  or  5J  barrels  to  equal  1  ton  of  coal;  so 
that  at  90  cents  per  barrel  for  oil,  it  is  equal  in  heat-unit  value  to  coal 
at  $4.80  per  ton;  but  where  coal  is  dear  and  oil  as  low  as  50  cents 
per  barrel,  it  is  equal  to  coal  at  $2.60  per  ton,  and  in  locations  where 
€oal  is  about  $6  per  ton  the  difference  in  favor  of  oil  is  very  apparent. 

The  burners  or  injector-nozles  are  made  in  a  variety  of  forms; 
but  all  operate  on  the  same  principle.  The  steam-and-air  method  of 
atomizing  the  oil  has  not  as  yet  become  assured  as  to  the  use  of 


44    GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 

one  or  both  combined,  but  so  far  the  practice  has  favored  steam  as 
the  atomizing  agent,  with  an  indraught  of  air  by  the  force  of  the  jet. 
A  combined  steam-and-air  jet  or  an  air-jet  alone  requires  the  use  of 
an  air-compressor,  and  if  such  is  installed  with  independent  power 
the  steam  can  be  left  out  of  the  process  with  the  most  economical 
results,  for  the  steam  requires  a  high  temperature  added  before 
dissociation,  and  only  then  returns  its  absorbed  heat  by  the  reunion 
of  its  hydro-oxygen  elements. 

There  is  quite  a  wide-spread  misconception  regarding  the  part 
that  the  steam  which  is  used  for  atomizing  purposes  plays  in  effecting 
combustion.  It  is  supposed  by  many  that  after  atomizing  the  oil 
the  steam  is  decomposed  and  that  the  hydrogen  and  carbon  are  again 
united,  thus  producing  heat  and  adding  to  the  heat  value  of  the  fuel. 
While  it  may  be  true  that  the  presence  of  steam  may  change  the 
character  and  sequence  of  the  chemical  reaction,  and  result  in  the 
production  of  a  higher  temperature  at  some  part  of  the  flame,  such 
an  advantage  will  be  offset  by  lower  temperatures  elsewhere  between 
the  grate  and  the  base  of  the  stack.  All  steam  which  enters  the  fur- 
nace will,  if  combustion  is  complete,  pass  up  the  stack  as  steam,  also 
carrying  with  it  a  certain  quantity  of  waste  heat.  The  amount  of 
this  waste  heat  will  depend  upon  the  amount  of  steam  and  its  tem- 
perature at  the  entrance  of  the  furnace.  The  quantity  of  available 
heat,  measured  in  thermal  units,  is  undoubtedly  diminished  by  the 
introduction  of  steam.  In  an  efficient  boiler  it  is  quantity  of  heat 
rather  than  intensity  that  is  wanted.  For  many  manufacturing 
purposes  intensity  of  heat  may  be  of  primary  importance,  but  in  a 
steam-generator  a  local  intense  heat  is  objectionable  on  other  grounds 
than  those  of  economy,  viz.,  its  liability  to  cause  leaky  tubes  and 
seams  from  the  unequal  expansion  of  heating-surfaces. 

In  a  series  of  naval  official  trials  with  crude-petroleum  fuel,  the 
following  conclusions  were  arrived  at : 

"  a.  That  oil  can  be  burned  in  a  very  uniform  manner. 

"6.  That  the  evaporative  efficiency  of  nearly  every  kind  of  oil  per 
pound  of  combustible  is  probably  the  same.  While  the  crude  oil 
may  be  rich  in  hydrocarbons,  it  also  contains  sulphur,  so  that,  after 
refining,  the  distilled  oil  has  probably  the  same  calorific  value  as  the 
crude  product. 


GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS    45 

"  c.  That  a  marine  steam-generator  can  be  forced  to  even  as  high 
a  degree  with  oil  as  with  coal. 

"  d.  That  up  to  the  present  time  no  ill  effects  have  been  shown 
upon  the  boiler. 

"  e.  That  the  firemen  are  disposed  to  favor  oil,  and  therefore  no 
impediment  will  be  met  in  this  respect. 

"  /.  That  the  air  requisite  for  combustion  should  be  heated  if  pos- 
sible before  entering  the  furnace.  Such  action  undoubtedly  assists 
the  gasification  of  the  oil-product. 

"  g.  That  the  oil  should  be  heated  so  that  it  can  be  atomized  more 
readily. 

"  h.  That  when  using  steam  higher  pressures  are  undoubtedly  more 
advantageous  than  lower  pressures  for  atomizing  the  oil. 

"  i.  That  under  heavy  forced-draught  conditions,  and  particularly 
when  steam  is  used,  the  board  has  not  yet  found  it  possible  to  prevent 
smoke  from  issuing  from  the  stack,  although  all  connected  with  the 
tests  made  special  efforts  to  secure  complete  combustion.  Particularly 
for  naval  purposes  is  it  desirable  that  the  smoke  nuisance  be  eradicated, 
in  order  that  the  presence  of  a  warship  may  not  be  detected  from 
this  cause.  As  there  has  been  a  tendency  of  late  years  to  force  the 
boilers  of  industrial  plants,  the  inability  to  prevent  the  smoke  nuisance 
under  forced-draught  conditions  may  have  an  important  influence  upon 
the  increased  use  of  liquid  fuel. 

"  j.  That  the  consumption  of  liquid  fuel  cannot  probably  be  forced 
to  as  great  an  extent  with  steam  as  the  atomizing  agent  as  when  com- 
pressed air  is  used  for  this  purpose.  This  is  probably  due  to  the 
fact  that  the  air  used  for  atomizing  purposes,  after  entering  the  fur- 
nace, supplies  oxygen  for  the  combustible,  while  in  the  case  of  steam 
the  rarefied  vapor  simply  displaces  air  that  is  needed  to  complete 
combustion. 

"  k.  That  the  efficiency  of  oil-fuel  plants  will  be  greatly  dependent 
upon  the  general  character  of  the  installation  of  auxiliaries  and  fit- 
tings, and  therefore  the  work  should  only  be  intrusted  to  those  who 
have  given  careful  study  to  the  matter,  and  who  have  had  extended 
experience  in  burning  the  crude  product.  The  form  of  the  burner 
will  play  a  very  small  part  in  increasing  the  use  of  crude  petroleum. 
The  method  and  character  of  the  installation  will  count  for  much, 
but  where  burners  are  simple  in  design  and  are  constructed  in  ac- 


46  GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 


cordance  with  scientific  principles  there  will  be  very  little  difference 
in  their  efficiency." 

It  may  be  further  said  that  the  heat  of  steam  at  high  boiler- 
pressure  adds  greatly  to  the  atomizing  effect  by  heating  the  oil  in  its 
passage  through  the  injector  and  thus  vaporizing  its  more  volatile 
constituents;  whereas  the  cooling  effect,  by  the  expansion  of  com- 
pressed air,  would  have  an  opposite  effect,  unless  the  compressed 
air  could  be  highly  heated  by  passing  through  a  coil  in  the  smoke- 
chamber. 

P E T R O L E U M - O  I  L     BURNERS 

In  Fig.  23  we  illustrate  an  oil-  and  air-burner  in  which  the  oil 
enters  by  the  pipe  A  to  the  central  nozle  with  its  regulating-valve  C. 

The  compressed  air  enters  through  the 
pipe  B  and  issues  through  an  annular 
nozle,  and  is  retained  by  an  outer  nozle 
which  may  be  more  or  less  extended  for 
a  thorough  atomization  of  the  oil. 

A  burner  of  English  origin  is  shown 
in  Fig.  24,  for  the  combined  use  of  oil, 

FIG.  23.-011-  and  air-burner.       steam>  and   air>  which   are  combined  in 

an  expanding  nozle.     The  oil  enters  by 

the  rear  pipe,  and  its  flow  is  regulated  by  a  needle-valve.     Steam 
enters  by  the  middle  pipe,  forming  an  annular  jet  around  the  oil,  while 


FIG.  24. — Oil-,  steam-,  and  air-burner. 

the  air  enters  by  the  large  pipe  and  forms  an  annular  jet  surrounding 
both  oil  and  steam  as  the  combination  enters  the  expanding  nozle. 

In  Fig.  25  is  shown,  in  plan  and  section,  an  oil-burner  used  on  the 
locomotives  of  the  Southern  Pacific  railroads. 


GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS  47 

It  is  a  combined  oil-,  steam-,  and  air-burner  with  a  wide,  thin  mouth 
and  chambers  closed  at  the  sides,  so  that  the  compartments  are 


FIG.  25. — Flat-nozle  burner. 

separated  in  tiers,  one  above  the  other.     Oil  flows  along  the  flat  top 

chamber,  with  the  steam  in  the  central  chamber  to  heat  the  oil,  and 

the  oil,  steam,  and  air  meet  at  the 

end  of  the  inner  nozle,  where  the 

oil   is   atomized   in   contact   with 

the  air  and  steam  and  projected 

through  the  end  nozle. 

In  Fig.  26  is  illustrated  the 
Urquhart  type  of  burner,  in  use  on 
the  Russian  railways.  It  is  a  com- 
bined oil-,  steam-,  and  air-burner. 
Steam  enters  the  hollow  valve-spin- 
dle through  side-ports,  while  the  oil 
enters  by  a  side-pipe  and  through  an  annular  aperture  outside  of  the 
steam,  the  nozle  of  which  extends  into  a  hollow  stud  between  the 
plates  of  the  boiler-front.  A  plate  held  off  from  the  boiler  carries 
the  injector  with  an  air-space  to  give  air  to  the  jet  in  the  stay-tube. 

The  Oil  City  burner  (Fig.  27)  is  of  the  oil  and  steam  combination 
type,  with  a  cap  over  the  end  for  inducing  a  draught  of  air  around 
the  oil-  and  steam-jet.  The  nozle  is  made  long  that  the  steam  on  the 
outside  of  the  oil-nozle  heats  the  oil  for  more  perfect  atomization. 
The  oil-  and  steam-flow  are  both  adjustable  by  valve- wheels. 

The  F.  M.  Reed  burner  (Fig.  28)  is  somewhat  novel  in  the  manner 
of  combining  the  oil,  steam,  and  air. 

The  oil-flow,  regulated  by  an  outside  valve,  enters  through  the 


FIG.  26. — Urquhart  burner. 


48  GENERATION  OF  STEAM— FURNACES  AND  THEIR  ADJUNCTS 

valve-spindle,  surrounded  by  steam  from  a  side  entrance,  both  issuing 
through  a  short  expanding  nozle  into  a  chambered  nozle,  which 


FIG.  27. — Oil  City  burner. 

completes  the  atomizing  of  the  oil;  outside  of  this  is  a  larger  chambered 
nozle  through  which  air  is  drawn  by  the  force  of  the  jet,  and,  mixing 


FIG.  28.— F.  M.  Reed  burner. 

with  the  atomized  oil  and  steam,  the  final  issue  to  the  furnace  is  ready 
for  complete  combustion. 


CHAPTER    IV 


TYPES   OF   BOILERS 

ONE  of  the  earliest  types  of  the  modern  water- tube  boiler  was 
made  in  1804  by  John  Stevens  at  Hobo  ken,  N.  J.,  and  with  its  twin- 
screw  propellers  is  now  preserved  in  the  Stevens  Institute  as  the  cen- 
tury memento  of  our  present  water- 
tube  boilers  and  of  the  principles  of 
twin-screw  propulsion.  After  forty 
years  the  same  boiler,  engine,  and 
screws  were  placed  in  a  boat  of  the 
original  dimensions  and  propelled  at 
the  rate  of  eight  miles  per  hour. 

Boilers  of  the  shell  type  continued 
in  use  as  standard  form  during  the 
nineteenth  century,  with  an  occa- 
sional interpolation  of  a  water-tube  boiler,  a  flash-boiler,  and  inter- 
circulating  coil-boilers,  as,  for  example,  the  Perkins  type,  which  carried 
steam  at  1,000  pounds  pressure  per  square  inch  and  was  applied  to 
a  steam-gun  which  was  exhibited  in  New  York  in  1839  and  operated 
by  the  author. 

The  most  simple  form  of  boiler  is  the  long,  plain  shell  now  much 
used  on  sugar-plantations,  and  under  which  bagasse  is  used  for  fuel. 


FIG.  29. — Stevens  boiler. 


FIG.  30. — Cylinder  boiler. 

These  boilers  are  usually  set  in  nests  hanging  from  beams  supported 
by  the  side  walls,  and  are  closed  in  at  their  half-diameter.  Their 
boiler-power  may  be  computed  at  one-half  their  shell-area  divided  by 

10  per  horse-power. 

49 


50 


TYPES  OF  BOILERS 


The  double-flue,  cylindrical  shell-boiler  was  a  favorite  form  with 
wood-burning   furnaces   for   steam-boats    and   wood-working    mills, 


FIG.  31. — Double-flue  boiler. 

and  is  still  in  use  in  modified  forms.     One-half  the  shell-  and  all  the 
flue-surface,  divided  by  11,  equal  the  boiler  horse-power. 

The  internally  fired  flue-boiler  is  now  becoming  antiquated  from 
its  limited  furnace  capacity,  and  has  finally  merged  into  the  cor- 
rugated tubular  furnaces  of  the  marine  type. 

The  horizontal  tubular  boiler  has  been  a  standard  type  for  three- 
quarters  of  a  century,  and  is  yet  the  leading  steam-maker  within  the 
range  of  its  allotted  pressure.  For  ease  of  care  and  convenience  of 

repair  it  stands  at  the  head 
of  the  list  in  number  in  use 
in  all  countries.  When  well 
proportioned  for  its  work 
its  economy  is  unchallenged, 
and  at  pressures  of  100 

FIG.  32.-Cylindrical  tubular  boiler.  POUnds>    and    Under>    'li     ls> 

when  well  constructed  and 
cared  for,  as  safe  from  rupture  as  other  types. 

One-half  the  shell-  and  all  the  outside  tube-surface,  divided  by 
14,  equal  the  boiler  horse-power. 

The  Galloway  boiler,  an  English  type,  has  a  cylindrical  shell  with 
an  oval  flue  and  is  internally  fired.  It  has  two  furnaces  which  merge 
into  a  combustion-chamber  at  the  rear.  This  chamber  is  fitted  with 


FIG.  33. — Galloway  boiler. 


TYPES  OF  BOILERS 


51 


tapered  water-tubes  for  the  purpose  of  increasing  the  effective  heat- 
ing-surface of  the  boiler  and  of  promoting  a  better  circulation  of  water; 
they  also  act  as  stays,  largely  increasing  the  strength  of  the  flue  to 
which  they  are  fitted. 

The  heated  gases  after  passing  through  the  internal  combustion- 
chamber  return  along  the  outside  of  the  shell  to  the  front  and  again 
to  the  rear  end  and  to  the  chimney.  It  is  considered  an  efficient 


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FIG.  34. — Plan  and  section  of  boiler-setting. 

boiler.  All  the  internal  surface  of  flue  and  tubes  and  the  shell  exposed 
to  heat,  divided  by  12,  equal  the  boiler  horse-power. 

The  setting  and  care  of  a  cylindrical  tubular  boiler  are  matters 
of  careful  consideration.  Air-leaks  in  the  brickwork  adulterate  the 
hot  gases  of  combustion  and  are  the  cause  of  fuel  loss;  so  that  too 
much  pains  cannot  be  taken  in  making  the  joints  as  close  as  the  bricks 
will  allow  and  fully  flushing  every  joint  with  mortar. 

Fig.  34  shows  the  plan  and  elevation  of  a  flush-front  boiler-setting 
with  a  filled-in  rear  chamber  and  recesses  for  catching  the  light  ashes 
that  pass  over  the  bridge-wall.  The  air-space  in  the  walls  is  shown 
in  the  cut  much  wider  than  needed,  as  2  inches  is  wide  enough  for 
the  largest  boilers. 


52 


TYPES  OF  BOILERS 


The  filling  of  the  rear  chamber  is  of  doubtful  value,  as  the  large 
area  of  this  chamber  serves  as  a  setting-place  for  the  light  ashes  that 


D 


m 


FIG.  35. — Section  with  flush  front,  open  chamber. 

are  carried  over  the  bridge-wall,  and  the  large  volume  of  hot  gases 
and  ashes  is  a  strong  radiant  of  heat  to  the  rear  end  of  the  boiler. 

In  Fig.  35  is  a  section  with  solid  brick  walls  carried  above  the  top 
of  the  boiler  and  with  an  extension  of  the  grate-surface  onto  the 
bridge-wall  and  a  support  of  the  back-chamber  closure  by  a  T  beam. 


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FIG.  36. — Plan  and  section  of  overhang  boiler-front  setting. 

Domes  on  this  type  of  boiler  are  not  recommended,  because  they 
are  a  source  of  weakness;  but  they  have  their  advocates  on  the  plea 


TYPES  OF  BOILERS 


53 


that  they  are  steam-reservoirs  and  promoters  of  dry  steam.  A  trifle 
larger  shell  and  a  dry  pipe  at  the  same  cost  is  the  safe  and  preferable 
plan. 

Fig.  36  shows  the  plan  and  section  of  the  setting  of  a  boiler  with 
an.  overhang  front  smoke-chamber,  which  rests  on  a  half -front  frame. 


THE     ROBB-MUMFORD     BOILER 

This  internal-fired  cylindrical  boiler  is  a  recent  type  of  construc- 
tion,  with   an   internal   fire-box  of   the  Morrison   corrugated   type 
and  with  its  full  area  of  head  filled  with  tubes;  the  lower  shell  is 
inclined,  as  is  also  the  steam- 
drum  above,  in  order  to  facilitate 
water-circulation.     The  design  is 
very  compact  and  enclosed  in 
a  brick-lined  metal  casing.     It 
appears  to  be  a  good  steamer. 
The    fire-surface    of    the   tubes, 
fire-box,  and  all  of  the  shell  ex- 


FIG.  37. — Internal  fired,  cylindrical  tub- 
ular boiler. 


posed   to  heat,  divided  by  12, 
equal  the  boiler  horse-power. 

The  "Continental  type"  of  marine  boiler  has  a  double  corrugated 
tubular  furnace  with  cylindrical  shell  and  re  turn- tubes.  This  form 
of  construction  is  the  general  one  for  marine  use,  and  is  made  in  the 


FIG.  38. — Marine  boiler. 

large  units  with  multiple  furnaces.  It  is  a  modification  of  the  "Scotch 
boiler"  and  is  also  made  with  double  ends,  set  back  to  back  with 
common  or  separate  combustion-chambers. 


54 


TYPES  OF  BOILERS 


The  down-draught  system  of  combustion  as  applied  to  a  Hein  boiler 
is  shown  in  Fig.  39,  in  which  is  illustrated  the  Hawley  furnace;  c  is  a 

tubular  grate;  d,  tube-connec- 
tion between  the  grate-header 
and  front  drum;  6,  tube-con- 
nection between  the  grate- 
header  and  rear  drum,  with 
blow-off. 

The  Hein  boiler  has  its 
water-legs  in  form  of  a 
wrought-iron  chamber  flanged 
and  riveted  to  the  steam- 
and  water-drums,  which  are 


FIG.  39. — Down-draught  furnace. 


FIG.  40. — Herreshoff  boiler. 


stayed  throughout  their  breadth.     The  tubes  are  expanded  in  the 
heads,  with  a  hand-hole  plate  opposite  each  tube  for  cleaning  and 
repairs.     Their  steaming  capacity  is 
about  11  feet  of  heating-surface  per 
boiler  horse-power. 

Among  the  many  pipe-boilers 
on  the  market  for  special  purposes 
and  claims  for  efficiency  and  high- 
pressure  safety,  we  illustrate  the 
Herreshoff  boiler  (Fig.  40) ,  which  has 
gained  much  credit  in  the  steam- 
yacht  service.  The  inner  coil  is  the 
evaporator  and  receives  the  feed- 
water  through  the  heater-coil  in  the  smoke-chamber.  The  conical 

coil  at  the  top  also  acts  as  a  heating-cham- 
ber and  feeds  the  inner  coil,  while  the 
outside  coil  is  the  superheater. 

A  separator-drum  at  the  side  entraps 
any  superfluous  water  that  may  be  fed  to 
the  boiler,  and  also  acts  as  a  separator, 
giving  to  the  superheater  dry  steam. 

The  Thornycroft  boiler  (Fig.  41)  is  shown 
FIG.  41.— Thornycroft  boiler.  .      .    ,       ,  ' 

as  a  type  in  principle  of  a  number  of  water- 
tube  boilers  on  the  market  in  Europe  and  the  United  States.  It 
consists  of  a  large  steam-drum  above  and  a  water-drum  below,  con- 


TYPES  OF  BOILERS 


55 


riected  with  a  large  number  of  bent  tubes.  The  water-return  is 
through  a  large  tube  at  the  rear  end  of  the  boiler.  The  same  princi- 
ple of  action,  with  different  de- 
signs in  construction,  is  carried 
out  in  the  Yarrow,  the  Moyes, 
and  the  See  water-tube  boilers, 
with  straight  tubes;  the  Boyer 
water-tube  boiler,  with  return 
bend  coils,  and  the  Meehan  and 
Sterling  water-tube  boilers,  with 
bent  tubes.  The  Du  Temple  ma- 
rine water-tube  boiler  (Fig.  42), 
made  in  France,  is  of  the  Thorny- 
croft  type  and  is  here  illustrated. 
Although  patented  in  1876  it 
has  all  the  essential  qualities  of 
the  later  water-tube  boilers.  A 
quick  and  powerful  steamer,  it 
has  been  much  in  use  in  the 


FIG.  42. — Du  Temple  boiler. 


FIG.  43. — Wood  vertical  water- 
tube  boiler. 


torpedo-boat  service.  Ample  circulation  is 
provided  for  by  the  direct  back  connections 
between  the  steam-  and  water-drums.  The 
cut  shows  a  half-section  of  each  side. 

We  do  not  deem  it  expedient  as  the 
object  of  this  work  to  illustrate  the  large 
number  of  boilers  on  the  market,  whose 
builders  claim  merit  and  public  favor  for 
their  special  designs;  nor  can  we  go  into 
the  merits  of  their  tests  of  economy  and 
usefulness  with  any  degree  of  safe  judg- 
ment; rather  let  their  work  with  users  tell 
the  story  of  their  worth. 

Among  the  vertical  water-tube  boilers 
with  straight  tubes  between  the  steam- 
and  water-drums  with  outside  furnaces  we 
illustrate  the  Wood  boiler  (Fig.  43),  which 


has  large  steam-  and  water-drums  with 


56 


TYPES  OF  BOILERS 


FIG.  44.— Cahall  boiler. 


stayed  heads;  the  tubes  are  arranged  in  front  and  back  sections  with  a 
brick  or  tile  partition  carried  up  from  the  lower  head  to  near  the 
top,  so  that  the  products  of  combustion  traverse  the  whole  length 
of  the  tubes  up  and  down  and  out  to  the  chimney  at  the  rear. 

The  arched  furnace  projects  at  the  front, 
and  the  whole  boiler  is  enclosed  in  brick 
walls.  Circulation  is  obtained  by  the  more 
active  upward  current,  with  its  steam  in  the 
fire  section  and  induced  down-flow  in  the 
rear  section. 

Another  design  is  the  Cahall  water-tube 
boiler  (Fig.  44)  with  straight,  nearly  vertical 
tubes  between  an  annular  steam-drum  at  the 
top,  through  which  the  smoke  passes,  and  a 
water-drum  at  the  bottom.  The  furnace 
and  combustion-chamber  project  outside  at 
the  front,  and  a  circulating-pipe  is  carried 
from  the  steam-drum  to  the  water-drum 
outside  of  the  brick  setting. 

In  Fig.  45  is  shown  the  duplex  water-tube  boiler  made  by  the 
Philadelphia  Engineering  Works.  This  boiler  has  straight  vertical 
tubes  between  a  pair  of  steam-  and  water-drums.  The  steam-drums 
are  connected  with  several  cross-pipes,  as 
shown  in  the  cut,  and  the  water-drums  are 
connected  by  a  single  neck.  A  brick  wall 
between  the  two  stacks  of  tubes  directs  the 
products  of  combustion  upward  through  the 
tube-stack  next  to  the  furnace  and  down 
the  opposite  stack  and  to  the  chimney. 
The  water-circulation  takes  the  same  course 
through  the  tube-stacks  and  drum-connec- 
tions. 

In  Fig.  46  is  a  section  of  the  Sterling 
water-tube  boiler,  which   consists  of  three 

upper  or  steam-drums  and  one  lower  or  mud-drum,  with  the  tube- 
ends  bent  so  that  all  of  them  can  properly  enter  the  drums. 

The  steam-spaces  of  all  the  upper  drums  are  connected,  while  the 
water-spaces  of  only  the  front  and  rear  drums  communicate.     The 


FIG.  45. — Duplex  boiler. 


TYPES  OF  BOILERS 


57 


drums  are  made  of  flange  steel,  while  the  tubes  are  lapwelded  steel, 
tested  at  1,500  pounds  pressure  per  square  inch.  These  drums  and 
the  tubes  form  the  boiler  proper. 

It  is  designed  to  be  a  safety-boiler,  and  the  absence  of  flat  sur- 
faces renders  stay-bolts  and  braces  unnecessary;  it  will  be  seen  that  a 


FIG.  46. — Sterling  water-tube  boiler. 

fire-brick  arch  is  built  over  the  grates  and  immediately  in  front  of  the 
first  section  of  tubes.  This  arch  absorbs  heat  from  the  fire  on  the 
grates  and  becomes  an  incandescent,  radiating  surface.  Tile  parti- 
tions are  so  arranged  that  the  hot  gases  pass  the  entire  length  of  the 
three  stacks  of  tubes. 

The  feed-water  enters  the  rear  upper  drum,  the  coolest  part  of  the 
boiler,  and  as  it  descends  to  the  mud-drum  is  gradually  heated  by  the 
gases,  passing  to  the  chimney  to  a  sufficient  extent  to  render  insoluble 
much  of  the  sediment  that  it  contains,  which  is  deposited  in  the  mud- 
drum  in  the  form  of  mud  or  sludge,  from  which  it  may  be  blown 


58 


TYPES  OF  BOILERS 


off.     The  mud-drum  is  protected  from  the  intense  heat  of  the  furnace 
by  an  ample  bridge-wall,  and  acts  as  a  settling-chamber. 

The  middle  drum  is  connected  to  a  supplementary  drum  by  a 
series  of  tubes  in  the  same  manner  as  the  others,  and  receives  the 

priming,  which,  falling  through  the 
tubes  to  the  lower  drum,  is  recon- 
verted into  steam  and  superheated. 
By  suitably  disposed  fire-tile 
partitions  or  baffle-walls,  the  gases 
from  the  furnace  are  led  first  up 
among  the  first  bank  of  tubes,  de- 
pending from  the  front  drum,  thence 
down  the  middle  bank,  thence  up 
the  rear  bank,  and  on  into  the 
chimney  at  a  reduced  temperature. 
In  this  long  and  circuitous  pass- 
age the  gases  come  in  contact  with 
all  the  tubes,  which  method  insures 


FIG.  47. — Sterling  water-tube  boiler. 


a  more  or  less  complete  delivery  of  their  heat  to  the  water. 

In  Fig.  48  is  illustrated  the  latest  style  of  the  Babcock  &  Wilcox 
water-tube  boilers,  the  most  compact  and  economical  design  of  all 
of  their  extensive  manufacture,  and  best  suited  for  generating  high- 
pressure  steam. 

The  vertical  header  style  has  the  same  general  features  of  construc- 
tion as  their  other  styles,  with  the  exception  of  having  the  tube-sheet 
side  of  the  header  "stepped"  so  that  the  header  may  be  placed  at 
right  angles  to  the  drum,  instead  of  having  it  inclined,  as  in  previous 
designs.  This  form  permits  of  a  shorter  brick  setting,  thereby  re- 
ducing the  cost  of  erection  and  the  floor-space  occupied. 

The  last  step  in  the  development  of  the  water-tube  boiler,  beyond 
which  it  seems  almost  impossible  for  science  and  skill  to  go,  consists  in 
making  all  parts  of  the  boiler  of  wrought  steel,  including  the  sinuous 
headers,  the  cross-boxes,  and  the  nozles  on  the  drum.  This  was 
demanded  to  answer  the  laws  of  some  of  the  Continental  nations,  and 
the  Babcock  &  Wilcox  Co.  have  at  the  present  time  a  plant  turning 
out  forgings,  as  a  regular  business,  which  have  been  pronounced  to  be 
"a  perfect  triumph  of  the  forgers'  art." 

One  of  the  important  points  in  the  generation  of  steam  is  that  it 


TYPES  OF  BOILERS 


59 


should  be  dry  as  it  leaves  the  boiler;  and  in  this  class  of  boilers  the 
large  disengaging  surface  of  the  water  in  the  drum,  together  with  the 
fact  that  the  steam  is  delivered  at  one  end  and  taken  out  at  the  other, 
secures  a  thorough  separation  of  the  steam  from  the  water,  even 
when  the  boiler  is  forced  to  its  utmost.  Most  tubular,  locomotive, 
and  sectional  boilers  make  wet  steam,  "priming"  or  "foaming  "  as  it 
is  called,  and  in  many  "superheating  surface"  is  provided  to  "dry 


FIG.  48. — Babcock  &  Wilcox  vertical  header-boiler. 


the  steam";  but  such  surface  is  always  a  source  of  trouble,  and  is 
incapable  of  being  graduated  to  the  varying  requirements  of  the 
steam.  No  part  of  a  boiler  not  exposed  to  water  on  the  one  side 
should  be  subjected  to  the  heat  of  the  fire  upon  the  other,  as  the  un- 
avoidable unequal  expansion  necessarily  weakens  the  metal  and  is  a 
serious  source  of  danger.  Hence  a  boiler  which  makes  dry  steam  is 
to  be  preferred  to  one  that  dries  steam  which  has  been  made  wet. 

The  vertical  cylindrical  tubular  boiler  is  a  convenient  type  for 
cramped  fire-room  space  and  for  portable  use.     It  is  most  suitable  for 


60 


TYPES  OF  BOILERS 


small  units  of  power,  but  is  not  considered  to  be  of  economical  form. 
We  illustrate   three  models  which  cover  their  essential  differences. 

First,  an  English  design  with  submerged 
tubes  and  enlarged  water-  and  steam-spaces,  and 
in  which  a  diaphragm  is  inserted  among  the 
tubes  to  divert  the  circulation  across  the  tubes 
and  clear  the  tube-head  from  accumulation  of 
steam. 

Secondly,  a  submerged-tube  vertical  boiler 
as  ordinarily  constructed,  in  which  all  the  tube- 
surface  and  the  surface  of  the  furnace  divided 
by  10  equal  the  boiler  horse-power. 

Thirdly,  the  one  more  commonly  in  use,  the 
through-tube  model,  in  which  the  upper  ends 
of  the  tubes  are  exposed  to  undue  temperature 
and  to  the  troubles  arising  from  overheating  the  upper  ends  and  tube- 
head,  which  condition  weakens  the  expanded  joints,  causing  leakage. 
This,  together  with  the  difficulty  of  cleaning  the  tubes  on  the  inside 
and  of  removing  the  scale  from  the  outside,  or  clearing  the  fire-tube 


FIG.  49. — Vertical  sub- 
merged-head boiler. 


FIG.  50. — Submerged-tube  vertical  boiler.          FIG.  51. — Vertical-tube  boiler. 


TYPES  OF  BOILERS  61 

sheet  from  scale  and  mud  that  fall  upon  it,  is  a  serious  drawback 
in  the  use  of  this  type  of  boiler,  except  for  temporary  or  portable 
necessity. 

The  water-surface  of  such  boilers  is  small  for  the  quiet  delivery  of 
steam;  foaming  is  waste,  and  they  should  not  be  forced  beyond  two- 
thirds  of  their  rated  power. 

THE     HORSE-POWER     RATING     O  F    "B  O  I  L  E  R  S 

The  work  of  a  boiler  to  convert  water  into  steam  requires  some 
unit  to  represent  its  general  efficiency  as  a  steam-producer.  The 
method  of  Watt,  now  abandoned,  was  the  evaporation  of  1  cubic 
foot  of  water  per  hour  to  equal  a  boiler  horse-power.  The  method 
of  to-day  is  one  that  figures  on  evaporating  30  pounds  of  water  per 
hour  from  100°  F.  and  at  70  pounds  gauge-pressure  as  equivalent  to  1 
boiler  horse-power.  This  standard  is  also  equivalent  to  the  evapo- 
ration of  34.5  pounds  of  water  per  hour  from  and  at  212°  F.  As  a 
boiler  can  in  no  way  develop  power  of  itself,  it  would  seem  that  to 
assign  to  it  the  term  "horse-power"  is  illogical,  because  economy  in 
the  use  of  steam  must  depend  upon  the  engine  alone,  and  economy 
varies  greatly  with  the  various  types  of  engines. 

The  term  "horse-power"  as  applied  to  a  boiler  seems  justified, 
however,  as  a  matter  of  convenience,  and  probably  conveys  as  in- 
telligent an  idea  as  to  the  power  the  boiler  is  able  to  furnish  as  any 
other  term. 

The  power  of  a  boiler  to  make  steam  depends  upon  the  amount 
of  heat  generated  in  the  furnace,  and  on  the  proportion  of  that  heat 
which  is  transmitted  to  the  water  in  the  boiler. 

The  amount  of  heat  liberated  through  combustion  depends  upon 
the  quality  of  the  fuel,  the  rate  of  combustion,  and  the  size  of  the  grate. 

The  rate  of  combustion  varies  with  the  draught,  quality  of  coal,  and 
the  skill  with  which  the  fire  is  handled.  As  a  general  rule  a  moderate 
rate  of  combustion  is  preferable,  as  the  combustion  is  more  likely  to 
be  complete  and  the  heating-surfaces  are  thus  permitted  to  take  up 
a  larger  portion  of  the  heat  produced,  while  if  the  combustion  is  too 
rapid  a  large  amount  of  heat  escapes  to  the  stack.  On  the  other 
hand,  when  the  combustion  is  too  slow  a  considerable  excess  of  air 
is  admitted  to  the  furnace  through  the  grates  and  the  loss  of  heat  by 
radiation  and  conduction  is  proportionately  increased. 


62 


TYPES  OF  BOILERS 


The  heating-surface  of  a  boiler  is  a  factor  which  also  requires 
consideration.  The  heating-surfaces  of  the  various  kinds  of  boilers 
differ  in  their  efficiency;  thus,  for  instance,  the  tubes  of  a  return 
tubular  boiler  are  not  equal  in  radiating  value  to  the  shell  for  equal 
areas.  Neither  can  both  ends  of  a  tube  be  of  equal  value,  as  the 
value  decreases  with  the  length  of  the  tube.  It  is  therefore  of  little 
advantage  to  have  the  length  of  the  tube  more  than  fifty  times  its 
diameter. 

The  rating  of  a  boiler  as  now  sold  is  figured  from  the  amount 
of  its  heating-surface,  allowing  from  11  to  12  square  feet  per  horse- 
power. It  is  evident  that  this  method  of  rating  is  an  invitation  to 
boiler-makers  to  increase  the  heating-surface  at  the  expense  of  the 
boiler  capacity. 

This  has  no  bearing  upon  the  power  that  can  be  obtained  from  a 
horse-power  of  the  boiler.  The  type  and  model  of  the  engine  in  its 
economy  of  steam  used  in  pounds  per  horse-power  are  the  real  factors 
that  give  the  value  in  power  that  can  be  obtained  from  a  boiler 
horse-power;  so  that  a  boiler  horse-power  divided  by  a  steam-engine 
horse-power  in  pounds  of  steam,  equals  the  steam-engine  horse-power 
available  per  boiler  horse-power. 


HEATING-    AND     G R A T E - S U R F A C E     FOR     BOILERS 

The  amount  of  heating-surface  per  horse-power  varies  very  much 
in  the  different  types  of  boilers  and  with  the  amount  of  fuel  burned 
per  square  foot  of  grate.  The  square  feet  of  heating-surface  and 

TABLE  VI. — APPROXIMATE  PROPORTION  OF  HEATING-SURFACE  AND  GRATE-SURFACE 

PER    HORSE-POWER,    ETC.,    OF  VARIOUS    TYPES    OF    BOILERS. 


Coal 

per 

Rela- 

Square feet 

square 

Rela- 

tive 

Heating- 

Pounds  of 

Pounds  of 

TYPE  OP  BOILER. 

of  heating- 
surface  per 
horse-power. 

foot  of 
heat- 
ing- 

tive 
econ- 
omy. 

rapid- 
ity of 
steam- 

surface per 
square  foot 
of  grate. 

coal  per 
square  foot 
of  grate. 

water  per 
pound 
of  coal. 

sur- 

ing. 

face. 

Water-  tube 

10  to  12 

3 

1    00 

1  00 

35  to  50 

12  to  20 

9  to  12 

Cylind'l  tubular. 

14  '    16 

.25 

.91 

.60 

25  '    35 

10       15 

8  '    11 

Vertical  tube  .... 

15  '    20 

.25 

.80 

.60 

25  '    30 

10       15 

8  '    10 

Locomotive 

12  '    16 

275 

85 

55 

50  '    100 

20       40 

8  '    11 

Flue    

8  '    12 

.4 

79 

.25 

20  '    25 

10       20 

8  '    10 

Plain  cylindrical  . 

6  '    10 

.5 

.69 

.20 

15  '    20 

15       25 

7  '    9 

TYPES  OF  BOILERS  63 

grate-surface  are  so  variable  in  the  various  types  and  many  designs 
of  the  same  type,  that  no  condition  as  to  actual  performance  or  effi- 
ciency of  any  boiler  can  be  made  except  as  deduced  from  the  actual 
work  of  one  of  its  own  type  and  model  under  equal  conditions  of 
operation. 

In  the  foregoing  table  are  values  nearly  covering  the  limits  of 
practical  work  with  various  types  of  boilers. 


THE     INDICATORS     OF     B  O  I  L  E  R  -  C  O  N  T  R  O  L 

The  safety-valve,  the  pressure-gauge,  and  the  water-gauge  are  the 
safety-indicators  of  all  steam-generators  and  as  such  are  to  be  watched 
with  all  the  care  of  the  engineer  as  indicating  what  is  the  condition 
between  the  furnace  and  the  engine. 

The  size  of  the  safety-valve  is  an  important  matter,  and  it  is  well 
to  consider  the  area  of  the  grate,  the  weight  of  fuel  burned,  and 
the  steam-pressure  when  calculating  the  required  area  of  a  safety- 
valve,  because,  other  things  being  equal,  the  volume  of  steam  gen- 
erated in  a  given  time  will  depend  upon  the  weight  of  the  coal  burned, 
and  the  velocity  of  escape  will  depend  upon  the  pressure. 

A  general  rule  or  formula  given  by  Professor  Thurston  is:  Area  = 

—  —  ,  in  which  w  =  weight  of  steam  made  per  hour  in  pounds,  and  p 

the  gauge-pressure.     Another  formula,  of  unknown  source,  is  based 

22  5G 

upon  the  grate-surface  and  gauge-pressure:  Area  of  valve  = 


in  which  G  =  grate-surface  in  square  feet;  p  =  gauge-pressure. 

When  the  area  of  the  grate  and  the  steam-pressure  are  not  con- 
sidered, 1  square  inch  of  valve-area  should  be  provided  for  each 
3  square  feet  of  grate-surface  for  spring-loaded  or  "pop"  valves, 
and  1  square  inch  of  valve-area  for  each  2  square  feet  of  grate- 
surface  for  the  lever-and-weight  variety.  A  safety-valve  should  be 
proportioned  for  the  lowest  regular  pressure  to  be  carried  because 
steam  of  higher  pressure  possesses  a  smaller  volume  and  escapes  at  a 
much  higher  velocity,  so  that  a  smaller  valve  will  discharge  the  same 
weight  of  steam  in  less  time;  therefore,  as  the  pressure  becomes  higher 
the  valve  may  be  made  smaller. 


64 


TYPES  OF  BOILERS 


In  the  following  table  are  given  the  safety-valve  areas  in  square 
inches  per  square  foot  of  grate  and  various  pressures  based  on  the 
velocity  and  weight  of  issuing  steam  at  the  different  pressures. 

TABLE   VII. — AREAS  OF  LEVER  SAFETY-VALVES  FOR  EACH  SQUARE  FOOT  OF 

GRATE-SURFACE. 


Gauge- 
pressure. 

Area  in 
square 
inches. 

Gauge- 
pressure. 

Area  in 
square 
inches. 

n               |    Area  in 
Gauge-          square 
pressure.  ;     £che* 

Gauge- 
pressure. 

Area  in 
square 
inches. 

15 

1.250 

65 

.468 

115 

.288 

165 

.208. 

20 

1.071 

70 

.441 

120 

.277 

170 

.202 

25 

.937 

75 

.416 

125 

.267 

175 

.197 

30 

.833 

80 

.394 

130 

.258 

180 

.192 

35 

.750 

85 

..375 

135 

.250 

185 

.187 

40 

.681 

90 

.357 

140 

.241 

190 

.182 

45 

.625 

95 

.340 

145 

.234 

195 

.178 

50 

.576 

100 

.326 

150 

.227 

200 

.174 

55 

.535 

105 

.312 

155 

.220 

225 

.166 

60 

.500 

110 

.300 

160 

.214 

250 

.158 

In  Fig.  52  is  shown  the  lever  safety-valve,  the  lever  of  which  is 
of  the  third  order.     0  is  the  fulcrum;  A  the  distance  from  the  fulcrum 

to  the  centre  of  the  valve;  B  the  dis- 
tance from  the  fulcrum  to  the  centre 
of  gravity  of  the  lever;  C  the  distance 
from  the  fulcrum  to  the  centre  of  the 
weight;  D  total  length  of  the  lever, 
and  S  the  diameter  of  the  valve-open- 
ing, all  in  inches.  G  =  the  weight  of 


FIG.  52. — Lever  safety-valve. 


the  lever  at  its  centre  of  gravity,  and  W  the  weight  of  ball;  V  =  the 
weight  of  the  valve  and  spindle;  P  =  pressure  in  pounds  per  square 

inch. 

w_S2X.7854xPxA-(GxB)-(VxA) 


C 


S2X.7854xPxA-(GxB)-(VxA) 
W 


In  Fig.  53  is  shown  a  differential  safety-valve  in  which  the  enlarged 
area  of  the  upper  valve  compensates  for  the  differential  tension  of 
the  spring  upon  opening  the  valve,  thus  causing  the  valve  to  open 
wide  without  increase  of  boiler-pressure. 

Another  form  of  spring  safety-valve,  known  as  the  "pop"  or  reac- 
tionary valve,  of  which  the  Ashcroft  is  .a  good  example,  is  one  in 


TYPES  OF  BOILERS 


65 


which  the  steam  issuing  from  under  the  valve  is  deflected  by  a  curved 
lip  or  flange  in  such  a  manner  as  to  cause  an  additional  pressure  by 
its  reaction  that  aids  effectively  in  raising  the  valve.  The  pressure 
at  which  a  "pop"  valve  will  blow  cannot,  as  a  rule,  be  as  closely 


FIG.  53. — Differential  safety-valve. 


FIG.  54.— "Pop"  safety-valve. 


estimated  as  with  the  lever-and-weight  style,  and  must  therefore  be 
finally  adjusted  by  trial.  Fig.  54  shows  a  section  of  the  consolidated 
pop  safety-valve  with  wing-guides.  The  seat  is  narrow  and  at  an 
angle  of  45°,  above  which  are  the  enlarged 
lipped  area  and  shield. 

Water-gauges  and  their  position,  with  the 
facilities  for  keeping  them  in  perfect  condition, 
are  essential  to  the  welfare  of  a  steam-plant. 
Their  length  should  correspond  with  and  cover 
the  range  of  water-level  assigned  for  the  different 
sizes  and  types  of  boilers.  In  all  cases  they 
should  be  fixed  to  water-columns  or  stand-pipes 
containing  the  gauge-cocks;  although  with  the 
ordinary  vertical  boilers  this  is  not  always  a 
fast  rule.  Their  pipe-connections  should  be  so 
arranged  that  dry  steam  enters  the  top  of  the 
water-column  and  water  enters  the  bottom  from 
a  quiet  part  of  the  boiler- water,  with  blow-off  FIQ  55._Quick_cios_ 
valves  for  both  water-column  and  water-gauge.  ing  water-gauge. 


66 


TYPES  OF  BOILERS 


A  water-column  should  be  blown  out  at  least  once  a  day,  and 
as  often  as  three  or  four  times  a  day,  depending  upon  the  quality  of 

the  feed-water  employed.  The  gauge- 
cocks  should  be  opened  after  blowing 
out  the  column  or  the  glass  to  see  that 
the  water-level  in  the  glass  tallies  with 
the  level  indicated  by  the  gauge-cocks. 

Pressure-gauges  should  as  a  rule  be 
placed  convenient  for  observation,  with 
the  shortest  piping  possible,  and  with  a 
siphon  beneath  the  gauge  for  its  protec- 
tion from  injury  from  steam  within  its 
spring.  A  cock  on  the  gauge  is  neces- 
sary, and  if  the  pipe  is  of  a  length  to  accumulate  water,  a  pet-cock  at 
its  lowest  point  near  the  gauge  serves  to  blow  out  any  sediment  and 
prove  the  proper  connection  of  the  gauge  with  the  boiler. 

One  of  the  most  satisfactory  and  convenient  instruments  for  the 
engine-room  or  office,  to  show  the  range  of  boiler-pressure  during  the 

daily  run,  is  an  Edson  recording 
steam-gauge,  which  we  illustrate 
in  Fig.  57  and  detail  in  Fig.  58. 
The  diaphragm  D  is  so  corru- 


FIG.  56. — Bourdon  gauge. 


FIG.  57. — Edson  recording  gauge. 


FIG.  58. — Section  of  gauge. 


gated  that  its  movement  under  pressure  shall  be  practically  uniform  for 
equal  increases  of  pressure.    From  this  diaphragm  a  connecting-rod,  G, 


TYPES  OF  BOILERS 


67 


actuates  a  small  crank,  H,  the  shaft  of  which  bears  an  open  segment, 
which  actuates  a  pinion  on  the  arbor  of  an  index  showing  the  pressure 
on  the  diaphragm.  At  the  same  time,  by  means  of  levers  H2,  H3, 
vertical  movement  is  communicated  to  a  pencil-point,  which  records 
gradually  on  a  graduated  paper  ribbon  the  pressure  shown  by  the 
index  as  being  on  the  diaphragm.  The  paper  strip  has  given  to  it  by 
clock-work  a  regular  motion  from  the  drum  K  to  K2,  and  has  marked 
on  it  vertical  spaces  corresponding  to  hours.  By  this  means,  not  only 
the  index-hand  shows  the  pressure  put  on  the  gauge,  but  the  pencil 
makes  a  continuous  record  showing  all  fluctuations  and  when  they 
occurred.  There  is  also  an  electrical-alarm  attachment  by  means  of 
which,  when  the  pressure  passes  a  certain 
limit,  a  bell  is  rung. 

Fusible  plugs  are  in  use  and  are  required 
by  law  to  be  applied  to  boilers  of  sea-going 
vessels.  They  are  generally  composed  of 
pure  Banca  tin,  which  melts  at  443°  F.,  in- 
cased in  a  brass  shield  and  screwed  into  the 
boiler-sheet  from  the  water  side  and  at  the 
highest  point  subject  to  exposure  to  the 
furnace-heat  by  low  water.  In  Fig.  59  is 
shown  an  inside  and  an  outside  fusible 
plug  of  the  model  required  by  the  United  States  Inspection  Service. 
No  composition  metal  is  allowed;  the  diameter  of  the  water-end  of 
the  tin  plug  is  about  one-half  inch. 

The  feed-pipe  should  enter  a  boiler  at  a  convenient  point  and  be 
so  arranged  on  the  inside  as  to  prevent  as  much  as  possible  the 
immediate  contact  of  the  feed-water  with  the  highly  heated  furnace- 
plates  or  hot  part  of  the  tubes.  There  are  many  designs  of  the 
arrangement  of  feed-  and  blow-off  pipes,  adapted  to  the  different 
types  and  models  of  boilers  in  use,  so  that  no  fast  rule  can  be 
quoted. 


FNSIDETYPE    OUTSIDE  TYPE 
FIG.  59. — Safety-plugs. 


STRENGTH    OF    CYLINDRICAL    S H E L L - B O I L E R S 

As  there  are  apprehensions  among  some  engineers  in  regard  to 
the  direction  of  the  strains  in  the  shell  of  a  cylindrical  boiler,  we  illus- 
trate in  Fig.  60  these  conditions,  which  are  shown  by  the  directions 


68 


TYPES  OF  BOILERS 


Diameter 


of  the  arrows  in  the  upper  and  lower  half  of  the  shell.  It  will  be  seen 
that  the  actual  direction  of  the  pressure  is  radial;  but  the  resultants 
of  the  directions  of  the  arrows  are  only  fully  effective  at  the  points  of 

their  angles  of  position  and  only  as  the 
sine  of  the  angle  for  any  single  collective 
point  in  the  circumference,  and  for  the 
diameter,  as  in  the  diagram;  the  results 
due  to  the  sines  of  the  radial  stresses  in 
the  upper  half  are  shown  in  the  direction 
of  the  arrows  in  the  lower  half  of  the 
diagram.  The  pressure  in  pounds  per 
square  inch,  multiplied  by  the  semidi- 
ameter  of  the  shell  in  inches,  equals  the 
strain  in  a  section  of  the  shell  1  inch 
wide. 

The  resistance  in  the  shell  is  the 

tensile  strength  per  square  inch,  multiplied  by  the  thickness  in  deci- 
mals of  an  inch  for  the  sheet  alone  and  an  allowance  made  for  the 
loss  in  strength  by  the  riveted  seam. 

For  single-riveted  seams  an  allowance  of  from  40  to  45  per  cent, 
of  the  tensile  strength  of  the  sheet  should  be  made  and  for  double- 


FIG.  60. — Strains  in  a  boiler-shell. 


c 
c 


->r- 


> 


FIG.  61. — Double-lap  joint. 

riveted  seams  an  allowance  of  33  per  cent. ;  making  their  tensile  strength 
55  and  67  per  cent,  of  that  of  the  plate.  The  strength  of  the  single- 
riveted  girt-seam  is  much  greater  for  any  size  shell  than  a  single-  or 
double-riveted  longitudinal  seam;  besides,  the  head-support  from  the 
tubes  is  fully  equal  to  the  strain  within  their  area.  The  strength  of 


TYPES  OF  BOILERS  69 

the  longitudinal  seam  in  all  forms  of  boiler-shells,  steam-drums,  riveted 
pipes  and  tanks,  determines  to  a  marked  degree  the  pressure  which 
the  structure  is  capable  of  carrying  continuously  and  with  safety. 
Boilers  are  now  so  generally  made  of  steel  plates  and  rivets  that 
we  give  some  details  of  the  make-up  of  these  seams.  In  Fig.  61  is 


it 


^m 

k» 


> 


FIG.  62.—  Triple-lap  joint. 


shown  the  lay-out  of  a  double-riveted  lap-joint  with  the  rows  staggered, 
which  is  the  strongest  joint  with  two  rows  of  rivets;  and  in  Fig.  62  the 
lay-out  of  a  triple-riveted  seam,  with  an  accompanying  table  of 
thicknesses  of  plates,  sizes  of  rivets  and  holes,  and  their  distance 
apart  ;  also  the  percentage  of  the  strength  of  the  seam  in  proportion 
to  the  strength  of  the  plate. 

TABLE  VIII.  —  PROPORTIONS  FOR  BOILER-JOINTS;  DOUBLE-RIVETED. 


DIAMETER. 

PITCH  OP  RIVETS. 

LAP  OP 
PLATES. 

PERCENTAGE  OP  JOINT. 

Thickness 
of 
plate. 

Rivet. 

Hole. 

hole  to 
of  plate. 

Centre  to  centre 
zigzag  riveting. 

Zigzag 
riveting. 

Steel  plate. 

Hori- 
zontal. 

Vertical. 

Iron 

Steel 

A 

A 

B                  C 

E 

F 

i 

| 

H 

I 

81 

H 

81 

72.48 

72.48 

H 

11 

2f 

1ft 

2f 

67.01 

71.46 

It 

1ft 

2| 

If 

2f 

62.54 

70.42 

ft 

it 

i 

1ft 

2£ 

59.44 

69.55 

I 

tf 

If 

21£ 

lai" 

21t 

58.44 

68.07 

ft 

11 

1 

1* 

3 

1^. 

3 

57.87 

66.65 

£ 

iiv 

lit 

3* 
8ft 

m 

ift 

56.46 
54.29 

66.00 
66.05 

* 

ll 

4 

3f 

i« 

3f 

54.42 

64.82 

70 


TYPES  OF  BOILERS 
PROPORTIONS  FOR  BOILER-JOINTS;  TRIPLE-RIVETED. 


i 

i 

i 

gl 

U 

5 

79.14 

80.34 

A 

i 

H 

8 

1A 

5f 

72.74 

79.25 

1 

• 

1 

8f 

if 

6| 

68.79 

78.37 

• 

1 

1A 

8| 

m 

6 

66.18 

77.46 

1 

• 

i 

if 

4 

6f 

64.39 

76.56 

F 

!J 

i 

1 

IA 

1 

28 

?! 

63.15 
62.27 

75.78 
75.04 

"H1 

1A 

It 

1^-4 

2-iV 

7| 

61.64 

74.27 

* 

It 

1A 

If 

4l 

8 

61.22 

73.63 

The  hydraulic  test  of  a  boiler  should  be  at  a  pressure  not  more 
than  one  and  a  half  times  the  working  pressure. 

TABLE  IX. — SAFE  WORKING  PRESSURE  FOR  WELL-MADE  CYLINDRICAL  TUBULAR 
BOILERS  WITH  STEEL  SHELLS;  DOUBLE-  AND  TRIPLE-RIVETED. 


Diam- 
eter. 

Thick- 
ness. 

Steel  shell. 
Iron  rivets. 

Steel  shell. 
Steel  rivets. 

Diam- 
eter. 

Thick- 
ness. 

Steel  shell. 
Iron  rivets. 

Steel  shell. 
Steel  rivets. 

36 

i 

Ill       121 

Ill      123 

56 

A 

82        89 

88          97 

A 

128      139 

137      151 

1 

92      101 

104      116 

38 

t 

105      115 

105      116 

58 

A 

79        86 

85        94 

A 

121       132 

129      144 

1 

89        98 

100      112 

40 

i 

100      109 

100      110 

60 

A 

77        83 

82        91 

A 

115      125 

123      136 

85        95 

97      108 

42 

i 

95      104 

95      105 

62 

1 

83        92 

94      104 

A 

110      119 

117      130 

A 

92      103 

108      120 

44 

i 

91        99 

91      100 

64 

1 

81        89 

91      101 

A 

105      114 

112      124 

A 

89      100 

105      117 

46 

i 

87        95 

87        96 

66 

1 

78        86 

88        98 

A 

100      109 

107      119 

A 

87        97 

102      113 

48 

A 

96      104 

102      114 

68 

1 

76        84 

86        95 

1 

107      118 

121      135 

A 

80        94 

99      110 

50 

A 

92      100 

98      109 

70 

f 

74        81 

83        92 

i 

103      113 

116      129 

A 

82        91 

96      107 

52 

A 

89        96 

95      105 

72 

t        1    72        79 

81        90 

1 

99      109 

112      124 

ft 

79        89 

93      104 

54 

A 

85        93 

91      101 

i 

89        98 

104      117 

1 

96      105 

108      120 

Perhaps  the  most  important  detail  in  boiler-construction  is  the 
bracing  of  flat  surfaces.  The  end-surfaces  of  steam-boilers  are  stayed 
by  means  of  braces  extending  from  the  heads  to  the  shell  or  by  longi- 
tudinal stays  extending  from  head  to  head.  In  all  flue-boilers  in 
which  the  flues  are  riveted  to  the  heads,  the  flues  themselves  act  as 
stays,  and  usually  have  strength  enough  to  dispense  with  other  stays 
below  the  water-line,  except  in  very  large  boilers  or  those  adapted 
to  very  high  pressures.  The  holding-power  of  wrought-iron  tubes 
expanded  in  the  heads  is  sufficient  to  withstand  any  working  pressure 


TYPES  OF  BOILERS 


71 


occurring  in  that  portion  of  the  boiler  in  which  the  tubes  are  lo- 
cated.    This  refers  especially  to  stationary  boilers. 

Flanging  the  edges  of  a  boiler-head  increases  its  stiffness  along 
the  outer  edge,  and  for  this  reason  2  inches  of  this  outer  flanged 


QOOOO'O'V'DDOOOO 

FIG.  63. — Stayed  boiler-head. 

surface  may  be  left  to  take  care  of  itself.  The  influence  of  the 
flange  extends  inward,  and  no  braces  need  be  located  within  4  inches 
of  the  flange  radius  for  pressures  less  than  150  pounds  per  square 
inch. 

The  holding-power  of  the  tubes  imparts  sufficient  stiffness  to  the 
boiler-head  not  to  require  braces  nearer  than  4  inches,  so  that  in  all 
ordinary  calculations  the  area  to  be  supported  would  be  represented 


FIG.  64. — Diagonal  and  direct  stay. 

by  the  segment  of  a  circle  (as  shown  in  Fig.  63)  of  6  inches  less  radius 
than  the  boiler-head  and  its  base-line  or  chord  4  inches  above  the 
tubes. 

The  location  of  the  stay-centres  is  not  easily  worked  out  except 
on  the  drawing-board,  but  the  area  to  be  stayed  in  any  given  case  can 


72 


TYPES  OF  BOILERS 


be  obtained  by  computation  of  the  area  within  the  lines  as  above  de- 
scribed. For  example,  for  a  boiler-head  58  inches  in  diameter  with 
a  required  braced  area  of  353.77  square  inches,  the  load  to  be  carried 
by  the  braces  will  be  equal  to  the  area  found  multiplied  by  the  maxi- 
mum safe  working  pressure  in  pounds.  If  the  pressure  is  to  be,  say, 
130  pounds  per  square  inch,  then  the  total  load  will  be  353.77  X 130  = 
45,990  pounds.  No  boiler-brace  should  be  allowed  a  greater  stress 
than  6,000  pounds  per  square  inch,  measured  at  the  smallest  part. 
The  number  of  braces  required  may  be  found  by  dividing  the  total 
load  by  what  one  brace  will  safely  carry,  which  in  this  case  is  45,990 
-T- 6,000  =  7.65,  say  8  braces;  that  is,  it  will  require  8  braces  having 
an  area  of  1  square  inch,  which  corresponds  to  about  1J  inches 
diameter. 

The  surface  or  area  supported  by  each  brace  is  found  by  dividing 
the  whole  area  to  be  supported  by  the  number  of  braces,  which  gives 


FIG.  65. — Gusset-brace. 

353.77-^8  =  44.22  square  inches.  The  square  root  of  this  number 
will  give  the  distance  between  the  braces  or  the  pitch,  which  is  6.64 
inches,  or  6^-  inches. 

Table  X  gives  the  proper  distance  between  the  stays  in  a  boiler  for 
different  maximum  pressures. 

The  table  gives  the  size  of  stays  corresponding  to  the  several 
pressures  when  the  stays  run  at  right  angles  to  the  head,  as  at  a  in 
Fig.  64;  but  when  they  are  placed  at  an  angle,  as  at  c,  their  holding- 
power  for  a  given  area  of  cross-section  is  considerably  reduced,  and 
in  order  to  maintain  the  holding-power  the  area  of  the  stays  must 


TYPES  OF  BOILERS 


73 


be  increased.  The  required  area  of  a  diagonal  stay  may  be  obtained 
by  dividing  the  area  of  the  direct  one  by  the  cosine  of  the  angle  that 
the  brace  bears  to  the  axis  of  the  shell. 

TABLE  X. — DIRECT  STAYS  FOR  BOILERS. 


Diameter 

Area, 

Working 

Number  of  inches  square  each  brace  will  sustain 
under  the  following  pressures: 

in  inches. 

inches. 

strength. 

-^               | 

75  Ibs. 

100  Ibs. 

125  Ibs. 

150  Ibs. 

1 

.60 

3,600  Ibs. 

7. 

6. 

5.4 

4.9 

.78 

4,712  ' 

7.9 

6.9 

6.1 

5.6 

H 

.99 

5,964  ' 

8.9 

7.7 

6.9 

6.4 

if 

1.23 

7,362  ' 

9.9 

8.6 

7.7 

7.0 

if 

1.48 

8,880  ' 

10.7 

9.5 

8.5 

7.7 

ii 

1.77 

10.620  ' 

11.9 

10.4 

9.2 

8.5 

The  stresses  in  boilers  and  the  constructive  details,  as  to  the 
strength  of  shells,  seams,  heads  and  braces,  are  given  here  as  belong- 
ing to  the  special  duties  and  practice  of  the  engineer,  as  an  inspector 
of  the  steam  plant  in  his  charge. 

There  is  much  more  that  might  be  written  in  regard  to  the  de- 
tails of  boiler  construction,  which,  for  the  information  of  engineers 
interested,  we  refer  to  works  treating  exclusively  upon  this  subject. 


CHAPTER    V 

BOILER-CHIMNEY   AND   ITS   WORK 

THE  power  of  a  chimney  to  create  draught  depends  somewhat 
on  its  form  as  well  as  height;  but  the  main  force  of  draught  is  in  the 
difference  of  outside  and  inside  temperatures.  The  ratio  of  wall-sur- 
face to  its  area  is  in  evidence  in  the  draught  problem;  and  in 
general  terms  a  round  chimney  is  first  in  efficiency  because  its  wall- 
surface  is  least  in  proportion  to  its  area,  the  ratio  being  for  equal 
areas  about  13  per  cent,  greater  wall-surface  in  a  square  chimney. 

Theoretically  the  strongest  draught  in  a  well-proportioned  chim- 
ney is  claimed  to  be  obtained  by  a  difference  of  absolute  temperatures 
of  25  to  12,  or  when  the  atmospheric  temperature  is  60°  and  the 
chimney  temperature  622°  F.  For  internal  chimney  temperatures 
above  622°  the  densities  of  the  gases  decrease  faster  than  the  velocity 
increases,  so  that  the  weight  of  the  gases  passing  up  the  chimney  is 
at  a  maximum  at  about  this  temperature;  but  the  draught-pressure 
increases  with  the  height  within  reasonable  limits. 

The  effective  area  of  a  chimney  varies  inversely  as  the  square 
root  of  the  height,  and  is  less  than  the  actual  area,  owing  to  the  friction 
of  the  gases  against  the  walls,  on  the  basis  that  this  is  equal  to  a 
layer  of  gas  2  inches  thick  on  the  wall-surface.  The  formula : 

0.3  H  /— 

Effectual   area  =     , also  equals  A  —  0.6  y  A,  in  which  H  is  the 

|/h 

boiler  horse-power,  h  height  of  chimney,  and  A  the  actual  area.  Also, 
the  boiler  horse-power_  of  a  chimney  may  be  computed  from  the 
formula:  H  =  3.33E  |/h,  and  the  height  for  any  horse-power  from 


-c- 


3   H\2 

J  ,  in  which  E  is  the  effective  area. 


The  diagram,  Fig.  66,  shows  the  draught  in  inches  of  water  for 
a  chimney  100  feet  high  with  different  temperatures  above  the  ex- 
ternal   atmosphere,   say  60°  F.     The  vertical  lines  represent  the 
chimney  temperatures  above  60°  F.  and  the  horizontal  lines  are  20  to  1 
74 


BOILER-CHIMNEY  AND  ITS   WORK 


75 


inch.  The  upper  curved  line  shows  the  ratio  of  the  flow  of  gases  at 
the  various  temperatures  along  the  vertical  lines  in  pounds  per  hour, 
which  may  be  computed  by  multiplying  the  height  of  the  curve  at 
any  given  chimney  temperature  above  that  of  the  atmosphere  by 


0     60     100    150    200    250    300    350    400    450    500    550    600    650    700    750    800 

FIG.  66. — Draught  and  weight  of  chimney-gases. 

the  vertical  scale  in  decimals  of  an  inch,  and  by  1,000  times  the  ef- 
fective area  in  square  feet,  and  by  the  square  root  of  the  height  in 
feet.  S  1,000  E  4/h  =  pounds  per  hour,  in  which  S  =  decimals  of  an 
inch  on  the  vertical  scale,  E  =  effective  area,  and  h  =  height  of  chimney. 
The  pressure-curve  in  decimals  of  an  inch  of  water  is  computed  from 

the  formula:  h  (-          -),  in  which  h  =  height  of  chimney  in  feet, 
\  ta      tc  / 

ta  is  the  absolute  temperature  of  the  air  entering  the  furnace,  and  tc 
the  absolute  temperature  of  the  chimney-gases. 

For  example,  for  a  chimney  100  feet  high  with  air  and  gas  tem- 
peratures of  60°  and  660°  F.,  100  (^-f%^)  =  -756  °f  an 
inch  water-pressure. 

From  this  formula  Table  XI  has  been  computed  for  external 
temperatures  of  from  10°  to  90°  F.,  and  for  chimney  temperatures 
from  240°  to  700°  F. 

For  any  other  height  of  chimney  than  100  feet,  the  water-pressure 
will  be  approximately  in  proportion  to  the  height,  so  that  the  pres- 
sures in  the  table  columns  at  the  junction  of  the  external  and  chim- 
ney temperatures,  multiplied  by  the  decimal  representing  the  pro- 
portion to  100  feet,  will  give  the  required  water-pressure. 

For  example,  for  the  respective  temperatures  of  60°  and  600°  F., 
and  160  feet  in  height,  1.6 X. 716  =  1.14  inches  water-pressure. 


76 


BOILER-CHIMNEY  AND  ITS   WORK 


TABLE  XI. — DRAUGHT-PRESSURE  IN  INCHES  OF  WATER. 
IN  A  CHIMNEY  100  FEET  HKJH. 


Temper- 
ature in 
chimney. 

Temperature  of  external  air.     (Barometer,  30  inches.) 

10° 

20° 

30° 

40° 

50° 

60° 

70° 

80° 

90° 

240° 

.488 

.451 

.421 

.388 

.359 

.330 

.301 

.276 

.250 

260 

.528 

.484 

.453 

.420 

.392 

.363 

.334 

.309 

.282 

280 

.549 

.515 

.482 

.451 

.422 

.394 

.365 

.340 

.313 

300 

.576 

.541 

.511 

.478 

.449 

.420 

.392 

.367 

.340 

320 

.603 

.568 

.538 

.505 

.476 

.447 

.419 

.394 

.367 

340 

.638 

.593 

.569 

.530 

.501 

.472 

.443 

.419 

.392 

360 

.653 

.618 

.588 

.555 

.526 

.497 

.468 

.444 

.417 

380 

.676 

.641 

.611 

.578 

.549 

.520 

.492 

.467 

.440 

400 

.697 

.662 

.632 

.598 

.570 

.541 

.513 

.488 

.461 

420 

.718 

.684 

.653 

.620 

.591 

.563 

.534 

.509 

.482 

440 

.739 

.705 

.674 

.641 

.612 

.584 

.555 

.530 

.503 

460 

.758 

.724 

.694 

.660 

.632 

.603 

.574 

.549 

.522 

480 

.776 

.741 

.710 

.678 

.649 

.620 

.591 

.566 

.540 

500 

.791 

.760 

.730 

.697 

.669 

.639 

.610 

.586 

.559 

550 

.835 

.801 

.769 

.738 

.698 

.679 

.652 

.625 

.600 

600 

.872 

.838 

.806 

.775 

.735 

.716 

.689 

.662 

.637 

650 

.906 

.872 

.840 

.809 

.769 

.750 

.723 

.696 

.671 

700 

.936 

.902 

.870 

.839 

.799 

.780 

.753 

.726 

.701 

051- 

o=- 


-> 


A  simple  form  of  draught-gauge  is  shown  in  Fig.  67.  It  consists 
of  a  small  glass  tube  bent  into  a  U  shape,  one-half  filled  with  water, 
with  a  scale  of  tenths  of  an  inch  fixed  between  the 
legs;  or  the  actual  difference  in  level  of  the  water 
may  be  measured  when  one  of  the  legs  is  connected 
to  the  chimney  by  a  tube.  Usually  a  piece  of  J-inch 
iron  pipe  is  passed  through  a  hole  in  the  main  flue 
and  connected  to  the  gauge  with  a  piece  of  rubber 
tube. 

The  size  and  height  of  a  chimney  and  its  boiler 
horse-power  depend  upon  the  amount  of  coal  assumed 
to  be  burned  per  horse-power,  which  requires  a  varia- 
ble size  and  height  to  meet  the  assumed  economy  of 
a  steam-plant. 

F     67  Table  XII  is  based  on  the  average  consumption  of 

Draught-gauge.     5  pounds  of  coal  per  hour  per  horse-power,  which  is 
assumed  to  be  the  maximum  amount  in  any  well- 
proportioned  power-plant.     For  any  less  amounts  of  coal  burned,  a 
reduction  in  chimney  height  and  area  or  an  increase  in  the  boiler- 


BOILER-CHIMNEY  AND  ITS  WORK 


77 


•saqoni  'A"aauiiqo 
8.renbs  jo  apis  ^uafBAtnbg 

O  Oi  <N  ^  I>  O  <N  *O  00  CO  00  ^  Ci  rH  O  *O      

HEIGHT  OP  CHIMNEY  IN  FEET. 

i 

i 
1 

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1 
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1 

1/5  QQ  ^H  4f  !>•  ^^  ^  GO  f^  c*"1 

i-H  rH  (N  C<T(N  COC*fc*f^  10 

i 

CO  iO  O  00  00  O5  OS  00  lr^  »O  i—  i 
'OOOCOOCiOCOOO^O'OCO 
(M  rfi  t>  O  <M  CO  O5  (M  O  "t1  CO 

•  ,-H  ^H  ,-H  (M  (M  (N  <M  evfcO1^  iff 

1 

So^S^g^oS^S^S0 

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rHi—  1  i—  li-H<M<N<NCOCO^lO 

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iO  l>  O5  i—  i  CO  »O  l>  O  CO  >O  Oi  <M  Oi  1> 

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CO  Tt<  »O  CO  00  O  C<J  -^  CO  00  i—  i  CO  CO  O5  O  CO 

iO 
(N 

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O  Tt<  00  00  O  CO  !>•  CO  O  O5  Ol  I-H  rf  O5      .... 
(M  C<1  (M  CO  ^O  CO  1>  O5  rH  (N  -^  !>  Oi  O     .... 

rH  rH  T-H  TH  i-H  (N       '       '       '       ' 

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8 

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^^coco^io^ooo^to^coooco^^ococoooogc^ 

•saqout  'aa^auretd 

2^^^gc?^^^^^ss^^^iis§^^^^ 

78  BOILER-CHIMNEY  AND  ITS  WORK 

horse-power  columns  may  be  made,  proportionable  to  the  amount 
of  coal  assigned  per  horse-power  hour. 

For  example,  for  a  power-plant  assumed  to  use  but  2J  pounds  of 
coal  per  horse-power  hour,  any  boiler-power  in  the  table  may  be 
divided  by  2,  and  its  amount  compared  with  other  chimney  sizes  and 
heights  for  selecting  the  required  size  and  height  of  chimney. 

The  formula  by  which  the  table  has  been  computed  is:  Boiler 
horse-power  =  (3.33A -0.6  /A)  /h,  or  3.33E  |/h;  E  =  A-0.6  |/A; 

(C\  QTT  \  2 
~]jr-)  ;  S  =  12  1/E  +  4,  in  which  A  =  area  of 

chimney  in  square  feet;  D  =  diameter  in  inches;  E  =  effective  area; 
S  =  side  of  square  chimney  of  equal  effective  area;  h  =  height  in  feet; 
H  =  horse-power. 

Fig.  68  is  an  example  of  a  steel  chimney  about  200  feet  high,  lined 
with  brick,  and  anchored  to  a  deep  foundation  by  12  long  bolts  1J 
inches  in  diameter.  It  is  13  feet  diameter  inside  and  equal  to  a 
draught  for  5,000  horse-power. 

Fig.  69  is  an  example  of  a  brick  chimney  of  varying  dimensions 
suitable  for  a  power-plant,  as  shown;  it  is  subject  to  details  suitable 
for  any  required  power. 

The  main  point  to  be  observed  in  the  construction  of  a  chimney 
after  the  height  and  internal  diameter  are  fixed,  is  its  stability  or  power 
to  resist  with  safety  the  overturning  force  of  the  highest  winds, 
which  requires  a  proportionate  relation  between  the  weight,  height, 
breadth  of  base,  and  exposed  area  of  the  chimney.     This  relation  is 

d  h2 
expressed  in  the  equation  C  — —  =  W,  in  which  d  =  the  average  breadth 

of  the  shaft;  h  =  its  height;  b  =  the  breadth  of  base — all  in  feet;  W  = 
weight  of  chimney  in  pounds,  and  C  =  a  coefficient  of  wind-pressure 
per  square  foot  of  area.  This  varies  with  the  cross-section  of  the 
chimney,  and  =  56  for  a  square,  35  for  an  octagon,  and  28  for  a  round 
chimney.  Thus,  a  square  chimney  of  average  breadth  of  8  feet,  10 
feet  wide  at  base  and  100  feet  high,  would  require  to  weigh  56  X8  X 100 
X 10  =  448,000  pounds  to  withstand  any  gale  likely  to  be  experienced. 
Brickwork  weighs  from  100  to  130  pounds  per  cubic  foot;  hence  such 
a  chimney  must  average  13  inches  thick  to  be  safe.  A  round  stack 
could  weigh  half  as  much,  or  have  less  base. 


I 

FIG.  68. — Steel  chimney. 


FIG.  69. — Brick  chimney  and  power-plant. 

79 


80  BOILER-CHIMNEY  AND  ITS  WORK 

The  external  diameter  of  a  brick  chimney  at  the  base  should  be 
one-tenth  the  height,  unless  it  be  supported  by  some  other  structure. 
The  "batter"  or  taper  of  a  chimney  should  be  from  yg-  to  J  inch  to  the 
foot  on  each  side. 


FIRING  AND  THE  CHIMNEY -DRAUGHT 

The  chimney-draught  is  one  of  the  first  things  to  be  studied  in 
the  design  of  a  power-plant,  since  upon  it  primarily  depend  the 
power  and  performance  of  the  boilers.  The  amount  of  fuel  that  can 
be  burned  in  a  given  time  on  a  square  foot  of  grate-surface  depends 
on  the  strength  of  the  draught,  and  draught,  coal  consumption,  and 
efficiency  are  so  closely  allied  that  a  discussion  of  one  naturally  brings 
in  the  others.  If  the  draught  is  poor  the  fires  have  to  be  carried  thin, 
and  in  this  way  a  larger  amount  of  air  than  is  necessary  for  the  combus- 
tion of  the  coal  comes  up  through  the  grates;  this  excess  air  is  not 
only  useless,  but  it  entails  a  loss  by  lowering  the  average  temperature 
of  the  furnace,  and  the  heat  will  not  transfer  to  the  water  so  rapidly. 
By  careful  nursing  a  heavy  fire  may  be  built  up  with  a  poor  draught, 
but  the  average  fireman  is  not  a  good  nurse;  he  will  either  poke  the 
fire  or  leave  it  alone,  and  his  ideas  of  when  to  do  these  necessary  parts 
of  firing  are  generally  as  nearly  right  as  are  the  ideas  of  many  of 
those  who  try  to  show  him  how.  Natural  draught  gives  its  best 
economy  with  a  low  rate  of  combustion,  and  as  a  general  rule  the 
fires  should  be  carried  as  thick  as  the  draught  will  burn  without  the 
fires  having  to  be  broken  up  more  than  once  an  hour.  The  stronger 
the  draught,  the  more  coal  can  be  burned  before  the  economical 
limit  is  reached. 

When  forcing  the  fires  with  a  strong  chimney-draught  there  is  the 
same  loss  as  with  thin  fires  and  poor  draught,  namely,  too  much  air 
per  pound  of  coal  burned,  and  another  and  greater  loss,  that  of  the 
increased  temperature  of  the  flue-gases  to  maintain  the  stronger 
draught;  for  after  the  temperature  of  the  flue-gases  exceeds 
600°  F.  it  takes  more  heat  to  strengthen  the  draught.  Under  the 
conditions  found  in  the  ordinary  plant  with  natural  draught,  the 
coal  burned  per  square  foot  of  grate-surface  per  hour  averages  from 
10  to  25  pounds,  and  the  air  used  per  pound  of  coal  runs  from  20  to 
30  pounds.  Twelve  pounds  of  air  per  pound  of  coal  is  all  that  is 


BOILER-CHIMNEY  AND  ITS  WORK  81 

required  for  its  complete  combustion,  and  the  average  plant  uses 
nearly  twice  this  amount.  Anything  that  will  cut  down  the  amount 
of  air  used  per  pound  of  coal  will  effect  a  saving.  The  most  that  can 
be  saved  in  this  way  is  about  5  per  cent,  of  the  coal. 

With  natural  draught  the  only  way  of  limiting  the  amount  of  air 
used  is  by  keeping  thick  fires.  But  thick  fires  are  apt  to  be  neglected, 
because  the  fireman  knows  that  if  the  steam  gets  down  he  can  stir  up 
the  fires  and  have  it  right  up  again,  while  he  would  manage  thin  fires 
in  a  better  manner,  because  he  cannot  take  any  chances  with  them. 
Furthermore,  there  are  some  kinds  of  coal  which  lie  on  the  grates 
like  sand,  and  it  is  impossible  to  get  enough  draught  with  a  chimney 
to  burn  a  thick  fire  of  such  coal. 

This  brings  us  to  a  consideration  of  some  of  the  kinds  of  forced- 
draught  apparatus.  When  speaking  of  forced  draught  the  general 
idea  is  that  the  air  supplied  by  a  fan  or  other  apparatus  will  cause  a 
higher  rate  of  combustion  of  the  coal  than  is  possible  with  the  rare- 
faction of  air  in  a  chimney.  This  was  the  practice  at  first,  but  forced 
or  induced  draught  is  now  used  for  all  rates  of  combustion.  When 
coal  is  dear  more  attention  is  paid  to  ways  of  burning  cheap  coal 
economically,  for  some  of  these  coals  will  evaporate  nearly  as  much 
water  as  high-priced  coal,  and  cost  less  than  half  as  much.  The 
cheapest  apparatus  for  this  purpose  is  some  form  of  steam-jet, 
either  one  that  produces  a  partial  vacuum  in  the  chimney,  as  in 
a  locomotive,  or  one  that  blows  into  a  closed  ash-pit  and  carries 
a  large  body  of  air  in  with  the  steam. 
But  on  account  of  the  large  amount  of 
steam  required  for  operation,  a  steam- 
jet  is  only  advisable  where  fuel  is  very 
cheap. 

In  Fig.  70  is  illustrated  one  of  many 
models  of  steam-jet  blowers,  with  an 
annular   cast-iron    chamber    perforated     FIG.  70. — Annular  steam-blower, 
for  steam-jets  at  an  angle  that  projects 

the  jets  in  a  converging  direction  that  draws  in  the  air  with  a  force 
corresponding  with  the  pressure  of  the  steam.  This  class  of  blowers 
are  much  in  use  and  are  connected  with  the  ash-pit  and  in  short 
chimneys  at  their  base. 


82 


BOILER-CHIMNEY  AND   ITS   WORK 


In  Fig.  71  is  illustrated  one  of  the  Korting  type  of  steam-blowers, 
with  a  double-nozle  air-inlet  and  double-cone  nozle  for  steam.  A 
needle-valve  regulates  the  flow  of  steam  from  the  central  jet,  which 


FIG.  71. — Korting  steam-blower. 

is  reenforced  by  the  combined  steam  and  air  in  the  larger  nozle,  by 
which  a  larger  volume  of  air  is  induced  and  expanded  in  the 
diverging-nozle. 

In  Fig.  72  is  illustrated  a  low-speed  fan-blower  of  large  volume 
and  force.  Its  particular  feature  is  in  the  narrow  curved  blades  set  in 
the  periphery  of  the  wheel  and  close  together,  which  prevent  local 
eddies  and  greatly  increase  the  efficiency  of  the  fan. 

A  well-designed  forced-draught  fan  will  run  with  less  than  1  per 
cent,  of  the  steam  supplied  to  the  engines,  while  the  amount  of  heat 


FIG.  72. — Sirocco  fan-blower. 


that  a  chimney  requires  for  its  operation  will  be  equal  to  30  per 
cent,  of  the  steam  supplied  to  the  engines.  Practically  it  is  impos- 
sible to  save  this  30  per  cent.,  on  account  of  the  cost  of  apparatus 
for  reducing  the  temperature  of  the  flue-gases  to  that  of  the  air  enter- 


BOILER-CHIMNEY  AND  ITS  WORK  83 

ing  the  ash-pit.  The  first  saving  a  fan-draught  will  make  is  in  the 
lessened  amount  of  air  per  pound  of  coal.  A  number  of  tests  have 
been  reported  where  the  air  supplied  was  less  than  15  pounds  to  each 
pound  of  coal.  The  temperature  of  the  furnace  with  a  lessened  air- 
supply  will  be  higher;  and  the  heat  will  be  more  quickly  transferred 
from  the  gases  to  the  water  of  the  boiler.  The  gases  will  travel  more 
slowly  over  the  heating-surface,  and  the  temperature  of  the  chimney- 
gases  will  be  lower.  Economizers  placed  between  the  boilers  and  the 
chimney  will  heat  the  feed-water  and  save  more  than  enough  to  pay 
for  themselves  in  a  short  time. 

The  use  of  hot  air  for  the  furnace  effects  a  saving  in  fuel,  and  with 
a  fan-forced  draught  taking  the  air  from  the  ceiling  or  roof  of  the 
boiler-  or  engine-room,  where  it  is  often  at  a  temperature  above 
100°  F.,  makes  a  saving  of  from  10  to  20  per  cent,  of  the  coal  over  the 
waste  from  a  low  natural  draught,  besides  the  comfort  of  a  modified 
temperature  of  the  room.  A  fan  should  be  large  enough  to  furnish 
the  required  amount  of  air  at  as  moderate  a  speed  as  will  give  the 
proper  pressure,  for  the  power  to  drive  a  fan  increases  as  the  cube 
of  the  speed. 

A  fan,  the  tips  of  its  blades  running  at  65  feet  a  second,  will  give  a 
draught  of  1  inch  of  water.  If  possible,  coal  should  not  be  burned 
with  a  stronger  draught  than  this,  for  with  a  stronger  draught  the  fires 
need  very  careful  watching  to  prevent  holes  from  burning  through 
and  letting  in  too  much  air,  although  mechanical  stokers  which  have 
a  constant-feeding  attachment  may  have  as  much  as  3  inches  of 
draught  without  affecting  the  economy,  for  a  strong  draught  will 
force  the  air  through  a  heavy  fire  in  more  intimate  contact  with  the 
fuel,  and  in  this  way  be  an  aid  to  perfect  combustion.  A  draught 
of  J  inch  of  water  is  about  as  low  as  it  is  possible  to  obtain  complete 
and  smokeless  combustion.  With  this  amount  of  draught  from  12 
to  20  pounds  of  coal  per  hour  per  square  foot  of  grate-surface  may 
be  burned. 


CHAPTER    VI 


HEAT-ECONOMY     OF     THE     FEED-WATER 

THE  saving  of  heat  that  would  otherwise  be  wasted  or  lost  by  the 
exhaust-steam  and  the  chimney-gases  is  of  great  consideration  in  the 
economy  of  steam-power.  The  exhaust-steam  water-heater  and  the 
chimney-heat  economizer  are  the  only  real  saving  devices  that  affect 
the  cost  of  fuel.  The  live,  steam  heaters  free  the  water  from  its 
incrusting  elements,  and  injectors  are  only  convenient  mechanical 
substitutes.  The  following  table  shows  the  saving  in  percentage  of 
the  total  fuel  used  by  heating  the  feed-water  between  various  initial 
and  final  temperatures: 

TABLE  XIII. — PERCENTAGE  OF  SAVING  IN  FUEL  BY  HEATING  FEED- WATER.      STEAM 
AT  70  POUNDS  GAUGE-PRESSURE. 


TEMPERATURE  TO  WHICH  FEED  is  HEATED. 


|i~ 

100° 

110° 

120° 

130° 

140° 

150° 

160° 

170° 

180° 

190° 

200° 

210° 

220° 

250° 

300° 

35°   J5.53 

6.38 

7.24 

8.09 

8.95 

9.89 

10.66 

11.52 

12.38 

13.24 

14.09 

14.95 

15.81 

19.40 

29.34 

40°    5.12  5.97 

6.84 

7.69 

8.56 

9.42 

10.2811.14  12.00  12.87 

13.73 

14.59  15.45  18.89 

28.78 

45° 

4.71i5.57 

6.44 

7.30 

8.16 

9.03 

9.90 

10.7611.6212.49 

13.36 

14.22  15.09  18.37 

28.22 

50°    4.30  5.16 

6.03 

6.89 

7.76 

8.64 

9.51 

10.3811.24J12.11 

12.98 

13.  85J14.  7217.  87127.  67 

55°    3.89 

4.75 

5.63 

6.49 

7.37 

8.24 

9.11 

9.99  10.85  11.73 

12.60 

13.  48;14.35 

17.38  27.12 

60° 

3.47 

4.34 

5.21 

6.08 

6.96 

7.84 

8.72 

9.60  10.47 

11.34 

12.22 

13V10  13.98 

16.  86)26.56 

65°    3.05  3.92 

4.80 

5.67 

6.56 

7.44 

8.32 

9.2010.08 

10.96 

11.84 

12.72 

13.60 

16.35  26.02 

70°    2.6213.50 

4.38 

5.26 

6.15 

7.03 

7.92 

8.80    9.68 

10.57 

11.45 

12.34 

13.22 

15.84125.47 

75°    2.19 

3.07 

3.96 

4.84 

5.73 

6.62 

7.51 

8.40    9.28 

10.17 

11.06 

11.95 

12.84 

15.33  24.92 

80° 

1.76 

2.65 

3  .  54 

4.42' 

5.32 

6.21 

7.11 

8.00    8.8 

9.78 

10.67 

11.57  12.46 

14.  81  '24.  37 

85° 

1.30  2.22 

3.11 

4.00 

4.90 

5.80 

6.70 

7.59 

8.48 

9.38 

10.28 

11.18  12.07 

14.32 

23.82 

90° 

0.89  1.78 

2.68 

3.58 

4.48 

5.38 

6.28 

7.18 

8.07 

8.98 

9.88 

10.7811.68 

13.82 

23.27 

95° 

0.45|l.34 

2.25 

3.15 

4.05 

4.96 

5.86 

6.77 

7.66 

8.57 

9.47 

10.3811.29 

13.31  22.73 

100° 

0.00 

0.90 

1.81 

2.71 

3.62 

4.53 

5.44 

6.35 

7.25 

8.16 

9.07 

9.98 

10.88 

12.80 

22.18 

The  feed-water  furnished  to  steam-boilers  has  to  be  heated  from 
the  normal  temperature  to  that  of  the  steam  before  evaporation  can 
commence,  and  this  generally  at  the  expense  of  the  fuel  which  should 
be  utilized  in  making  steam.  This  temperature  at  75  pounds  pressure 
is  320°  F.,  and. if  we  take  60°  F.  as  the  average  temperature  of  feed, 
we  have  260  units  of  heat  per  pound,  which,  as  it  takes  1.151  units  to 
evaporate  a  pound  from  60°  F.,  represents  22.5  per  cent,  of  the  fuel. 

84 


HEAT-ECONOMY  OF  THE  FEED-WATER 


85 


All  of  this  heat  therefore  which  can  be  imparted  to  the  feed-water  is 
just  so  much  saved,  not  only  in  cost  of  fuel  but  in  capacity  of  boiler. 
But  it  is  essential  that  it  be  done  by  heat  which  would  otherwise  be 
wasted.  All  heat  imparted  to  feed- water  by  injectors  and  live-steam 
heaters  comes  from  the  fuel  and  represents  no  saving. 

The  number  of  square  feet  of  surface  required  in  feed-water 
heaters,  for  each  horse-power,  assuming  an  abundance  of  exhaust- 
steam  is  available,  may  be  found  by  the  following  formula :  S  =  .227 

rp          rp 

log.  10  ™ — ^r,  in  which  S  =  square  feet  of  tube-surface  per  horse-power, 

Is  —  -1-2 

or  the  surface  required  to  heat  34.5  pounds  per  hour;  Ts  =  tempera- 
ture of  the  steam;  TI  =  temperature  of  the  water  entering  the  heater, 
and  T2  =  the  temperature  of  the  water  leaving  the  heater.  The  horse- 
power of  heater  per  square  foot  of  surface  is  l^S.  The  result 
obtained  by  the  use  of  the  formula  should  be  multiplied  by  1.12  for 
brass  tubes  and  by  1.67  for  iron  tubes. 

Table  XIV  gives  the  tube-surface  in  square  feet  required  to  heat 
34.5  pounds  of  water  per  hour,  or  for  each  boiler  horse-power. 

TABLE   XIV. — AREA  OF  HEATING-SURFACE    REQUIRED  IN  FEED-WATER  HEATERS 
PER  BOILER  HORSE-POWER,  34£  POUNDS  PER  HOUR. 

TEMPERATURE  OF  BOILER-FEED. 


170° 

180° 

190° 

200° 

Initial 

ature. 

Copper. 

Brass. 

Iron. 

Copper. 

Brass. 

Iron. 

Copper. 

Brass. 

Iron. 

Copper. 

Brass. 

Iron. 

50° 

.15 

.17 

.24 

.20 

.23 

.34 

.22 

.24 

.36 

.29 

.32 

.46 

60° 

.14 

.16 

.23 

.19 

.22 

.33 

.21 

.23 

.35 

.28 

.31 

.45 

70° 

.13 

.15 

.22 

.18 

.21 

.31 

.20 

.22 

.34 

.27 

.30 

.44 

80° 

.12 

.14 

.21 

.17 

.20 

.29 

.19 

.21 

.32 

.26 

.29 

.43 

90° 

.11 

.13 

.19 

.16 

.18 

.28 

.18 

.20 

.30 

.25 

.28 

.41 

100° 

.10 

.12 

.17 

.15 

.17 

.26 

.17 

.19 

.29 

.24 

.27 

.40 

110° 

.09 

.10 

.16 

.14 

.16 

.24 

.16 

.18 

.27 

.23 

.26 

.38 

120° 

.08 

.09 

.14 

.13 

.15 

.22 

.15 

.17 

.25 

.22 

.24 

.36 

130° 

.07 

.08 

.12 

.12 

.13 

.20 

.14 

.15 

.23 

.21 

.23 

.34 

The  extent  of  heating-surface  given  in  the  table  for  1  horse-power 
will  generally  be  found  ample  for  coil-heaters  and  for  horizontal 
double-flow  water-tube  heaters  having  copper  coils  and  copper  tubes 
respectively,  and  for  vertical  water-tube  heaters  with  corrugated 
copper  tubes  when  the  aggregate  tube-area  corresponding  to  the  direc- 
tion of  flow  is  not  large,  thus  insuring  a  more  rapid  circulation. 


HEAT-ECONOMY  OF  THE  FEED-WATER 


FEED-WATER     HEATERS 

Feed- water  heaters  are  made  of  both  the  closed  and  open  types. 
In  the  closed  type  the  water  is  caused  to  circulate  through  tubes 
arranged  in  different  ways,  while  the  exhaust-steam  envelops  the 
tubes  from  end  to  end  in  passing  from  the  inlet  to  the  outlet.  In 
other  heaters  of  the  closed  type  the  water  is  outside  and  the  steam 
inside  the  tubes.  The  former  method  of  heating,  however,  is  the 
better,  because  a  positive  and  more  rapid  circulation  of  the  water  is 
thus  secured;  and  it  has  been  found  that  the  efficiency  of  a  feed-water 
heater  depends  largely  upon  proper  circulation,  the  absorption  of 
heat  taking  place  more  rapidly  with  a  brisk  circulation  than  when  the 
circulation  is  sluggish.  Horizontal  tubes  frequently  give  somewhat 
better  results  for  a  given  area  of  heating-surface  than  do  vertical 
tubes,  but  the  slight  loss  due  to  the  position  is  fully  compensated 
for  in  the  vertical  types  by  allowing  slightly  more  surface  and  caus- 
ing the  water  to  flow  from  top  to  bot- 
tom against  the  current  of  steam,  so  that 
it  makes  but  little  difference  in  practice 
whether  a  horizontal  or  vertical  heater  is 
selected,  as  far  as  being  able  to  heat  water 
to  the  desired  temperature  is  concerned. 

When  certain  constructions  of  closed 
heater  are  employed,  notably  the  coil,  a 
somewhat  smaller  heater  may  be  used, 
owing  to  the  positive  and  rapid  circulation 
and  the  efficient  form  and  arrangement  of 
the  heating-surfaces.  The  closed  heater 
is  also  adapted  to  use  with  condensing- 
engines.  Either  type  may  be  successfully 
employed  in  connection  with  heating  sys- 
tems, the  shells  being  made  of  ample 

strength  to  resist  the  pressures  generally  employed  in  heating  by 
exhaust-steam.  The  temperature  of  the  water  leaving  the  heater  is 
usually  about  the  same  with  both  the  closed  and  open  types  under 
the  same  conditions.  The  shells  and  pipes  should  be  covered  with 
some  non-conducting  material  to  prevent  radiation,  so  that  as  much 


FIG.  73. — Multicoil-heater. 


HEAT-ECONOMY  OF  THE  FEED-WATER  87 

steam  as  possible  may  be  provided  for  other  purposes  when  the  steam 
is  to  be  utilized  after  passing  through  the  heater. 

The  open  heater  is  not  necessarily  subjected  to  any  pressure 
either  of  steam  or  water  except  that  due  to  the  weight  of  the 
water  it  contains.  This  type  of  heater  furnishes  a  settling-chamber 
for  the  impurities  in  the  feed-water,  which  with  muddy  water,  or 
water  containing  large  quantities  of  other  impurities,  is  of  great  ad- 
vantage. By  introducing  suitable  trays  or  pans  a  considerable 
quantity  of  scale-making  material  may  also  be  removed,  while  the 
condensation  of  a  portion  of  the  steam  furnishes  a  certain  amount 
of  pure  water,  which  is  added  to  that  in  the  heater.  One  of  the 
greatest  difficulties  formerly  experienced  with  open  heaters  was 
found  in  avoiding  the  effects  of  the  cylinder-oil  carried  into  the  heater 
by  the  exhaust-steam.  In  but  few  cases  at  present  is  this  difficulty 
experienced,  the  construction  being  such  as  to  exclude  the  greater 
part  of  the  oil,  and  to  give  the  water  sufficient  time  in  the  heater  to 
permit  the  remaining  oil  to  rise  to  the  surface  of  the  water  and  be 
drained  off  through  suitable  waste-pipes.  When  selecting  an  open 
heater  it  is  important  to  investigate  the  provisions  made  for  disposing 
of  the  oil  and  preventing  it  from  entering  the  boiler.  The  open 
heater  should  be  so  constructed  as  to  permit  easy  and  frequent  cleans- 
ing, when  necessary,  and  the  ready  removal  of  the  filtering  material 
and  of  pans  or  trays  when  these  are  employed. 

The  open  feed-water  heater  is  designed  so  that  the  water  entering 
at  the  top  will  be  finely  divided  and  will  fall  through  the  reservoir  of 
steam  in  the  form  of  a  fine  spray  or  a  very  thin  film,  thus  bringing 
practically  all  the  water  into  close  contact  and  causing  an  intimate 
commingling  with  the  steam  in  the  shortest  time  possible,  that  is 
when  considering  the  total  time  required  for  the  water  to  pass  through 
the  heater.  The  time  during  which  the  water  is  passing  downward 
from  the  inlet  to  the  water-reservoir  at  the  bottom  is,  however,  made 
as  long  as  possible  so  as  to  secure  the  thorough  absorption  of  the  heat 
in  the  steam,  for  upon  the  thoroughness  of  this  process  depends  the 
temperature  to  which  the  water  can  be  heated  with  a  given  initial 
temperature  and  a  given  temperature  of  steam. 

In  Fig.  74  is  a  sectional  view  of  the  Berryman  heater,  in  which  the 
exhaust-steam  passes  through  the  inverted  U-shaped  tubes,  which 


88 


HEAT-ECONOMY  OF  THE  FEED-WATER 


permits  both  ends  of  the  tubes  to  be  expanded  into  the  same  tube- 
sheet,  and  thus  they  cannot  be  affected  by  expansion  or  contraction. 
Each  tube  is  absolutely  independent  of  every  other  tube.  They 

seldom   coat   or  scale,  and   thus  their  full 
heating-surface  is  indefinitely  maintained. 

The  head,  into  which  the  tubes  are  set  is 
cast-iron,  from  2  to  3  inches  in  thickness. 
The  'holes  for  receiving  the  tubes  are  first 
drilled  the  size  of  the  inside  of  the  tubes, 
then  counterbored  to  within  \  inch  of  the 
bottom  of  the  tube-head,  leaving  a  solid 
shoulder  on  which  the  tube  rests.  A  groove 
is  cut  in  the  centre  of  the  bore  of  the  thick- 
ness of  the  tube.  The  U-shaped  tubes  are 
then  expanded  in  these  grooves,  their  shape 
preventing  any  strain  from  expansion  or 
contraction,  which,  together  with  the  man- 
ner of  setting  them,  prevents  leaking  or 
getting  loose. 

The  tube-head  is  concave,  and  at  its 
lowest  point  a  mud  blow-off  is  arranged, 
through  which  the  sediment  and  other  impurities  can  be  removed. 
It  should  be  opened  for  a  few  seconds  as  often  as  the  condition  of  the 
water  necessitates,  which  can  readily  be  determined  by  experiment. 

The  exhaust-steam  enters  at  one  side  of  the  heater,  passes  up 
through  the  tubes  and  down  and  out  on  the  other  side.  The  ports 
in  the  heater  may  be  arranged  to  meet  the  needs  in  any  case. 

The  water  enters  the  heater  at  the  side,  but  at  a  sufficient  distance 
from  the  bottom  to  prevent  disturbing  the  sediment  which  has  col- 
lected. 

The  water  leaves  the  heater  through  a  pipe  which  extends  down 
a  few  inches  from  the  top,  and  is  thus  taken  at  the  hottest  part. 

The  Wainwright  heater,  Fig.  75,  has  the  advantage  derived  from 
the  tubes  being  corrugated,  which  not  only  gives  increased  surface 
to  the  tubes,  but  makes  them  elastic,  and  thus  insures  their  tightness 
in  the  tube-heads.  There  is  an  ample  settling-chamber  at  the  bot- 
tom and  a  surface  blow-off  and  storage-room  at  the  top.  The  tubes 


FIG.  74. — Berry  man  heater. 


HEAT-ECONOMY  OF  THE  FEED-WATER  89 

occupy  only  one-fourth  of  the  shell-area,  and  the  net  shell-area  is  at 
least  three  times  as  large  as  the  area  of  the  exhaust-pipe.  This  allows 
the  steam  to  flow  freely  about  the  small  columns  of  moving  water. 

The  water-chambers  are  divided  into  several  compartments,  and 
the  partitions  are  so  arranged  that  they  direct  the  flow  of  the  feed- 
water  back  and  forth  through  the  heater,  using  the  various  groups  of 
tubes  in  succession,  with  a  consequent  increase  in  velocity  over  that 
obtained  in  the  non-return  type  of  heater.  Each  of  these  groups 
of  tubes  contains  a  sufficient  number  of  tubes  to  give  a  sectional 


FIG.  75. — Wainwright 
heater. 


FIG.  76. — Cookson  heater,  purifier, 
and  oil-separator. 


area  which  is  at  least  twice  the  sectional  area  of  the  feed-pipe.  This 
increase  in  the  speed  of  the  feed-water  brings  all  parts  of  it  into  con- 
tact with  the  heating-surface  and  insures  a  uniform  use  of  all  the 
tubes.  Experiments  have  shown  that  in  some  constructions  of  multi- 
tubular  heater  the  water  may  remain  almost  stagnant  in  a  portion 
of  the  tubes.  The  practical  result  is  that  there  is  offered  in  the  even 
flow  a  heater  with  which  there  can  be  a  very  high  final  temperature, 
approximating  212°  F.  under  ordinary  conditions  of  exhaust  with  non- 
condensing-engines. 

In  the  Cookson  heater,  Fig.  76,  the  steam  enters  the  side  and  strikes 
the  V-shaped,  oil-separating  plates  which  divide  the  volume  of  steam, 


90 


HEAT-ECONOMY  OF  THE  FEED-WATER 


the  ribs  on  the  plates  catching  the  oil  and  moisture  in  the  steam. 
The  steam  then  enters  the  enlarged  portion  of  the  exhaust- tube, 
where  it  passes  into  the  opposite  expansion  and  oil-separating  cham- 
ber and  discharges  into  the  atmosphere  or 
heating  system.  At  the  top  of  the  heater 
is  a  vent-pipe  for  carrying  off  the  air  re- 
lieved from  the  water  in  heating.  The 
vent-pipe  is  to  be  connected  with  the 
exhaust-outlet.  The  cold-water  supply  en- 
ters in  a  spray  and  condenses  the  steam, 
forming  a  partial  vacuum,  which  draws 
the  required  amount  of  steam  to  heat  the 
water  through  the  large  tube  in  the  centre. 
Only  that  amount  of  steam  necessary  to 
heat  the  water  comes  in  contact  with  it, 
the  remainder  passing  on  to  the  heating 
system  or  the  atmosphere. 

The  water-supply  is  connected  with  the 
water-inlet  valve,  which  is  opened  and 
closed  by  the  water-regulator,  maintaining 
at  all  times  a  uniform  water-level  in  the  heater.  The  water  entering 
the  spray-box  at  the  top  of  the  heater  overflows  in  a  spray  to  the  pan 
below,  and,  overflowing  this  pan,  falls  in  a  spray  into  the  next.  The 
water  passes  from  this  third  pan  over  its  outer  edge,  following  down  on 
the  under  side  to  the  next  pan  below,  and  so  on  down.  The  last  pan 
is  bolted  to  the  top  of  the  exhaust-tube.  The  water  sprays  from 
this  last  pan  to  the  water  below.  All  pans,  with  the  exception  of 
the  bottom  one,  are  loose,  made  in  halves,  and  are  readily  removed 
through  the  man-hole.  The  object  of  these  pans  is  to  catch  the  lime 
deposits.  The  water,  after  having  been  heated  in  direct  contact 
with  the  steam,  enters  the  hollow  partition  at  the  back  of  the  exhaust- 
tube.  The  water  discharges  from  the  hollow  partition  near  the  front 
into  the  filtering-chamber  below,  where  the  remaining  impurities  in 
suspension  are  removed  by  filtration.  The  filtering-chamber  is  filled 
with  coke  or  excelsior,  and  at  the  back  of  this  chamber  is  a  perforated 
plate  preventing  the  filtering  material  from  passing  through  to  the 
pump.  A  strainer-plate  is  also  placed  at  the  blow-off  connections. 
The  blow-off  and  oil-discharge  pipes  are  placed  on  the  side  opposite 


FIG.  77. — Feed-water  heater 
and  filter. 


HEAT-ECONOMY  OF  THE  FEED-WATER  91 

the  exhaust-inlet.  The  two  oil-separating  chambers  are  connected 
by  a  small  opening  through  the  hollow  partition  at  the  bottom, 
through  which  the  oil  and  condensed  steam  drain,  passing  from 
there  into  the  oil-discharge  pipe  and  thence  to  the  sewer. 

In  the  feed-water  heater  and  filter,  Fig.  77,  the  exhaust-steam 
enters  at  the  bottom  and  flows  into  the  first  compartment  through 
a  short  pipe,  thence  through  the  annular  opening  ^surrounding  the 
second  compartment  into  the  latter,  thence  through  another  annular 
opening  into  the  next  compartment.  After  passing  through  the 
annular  openings  the  steam  comes  in  contact  with  baffle-plates,  which 
direct  the  steam  through  the  falling  water  and  condense  it.  A  ring- 
pipe  at  the  top  distributes  the  water  upon  a  baffle-plate,  from  which 
it  falls  upon  the  top  filter  and  so  on  through  the  three  filter  sections. 

The  Hoppes  standard  feed-water  heater,  shown  in  Fig.  78,  is  sup- 
plied with  pans  of  the  same  design  as  those  in  the  live-steam,  feed- 
water  purifier.  The  water  in  flowing  over  the  sides  and  bottoms 


c- 

FIG.  78. — Hoppes  feed- water  heater. 

of  the  pans  comes  in  direct  contact  with  the  steam  and  is  heated 
nearly  to  the  temperature  of  the  exhaust-steam. 

This  heater  is  especially  designed  to  be  used  where  the  water  is 
bad,  and  one  peculiar  advantage  is  had  in  the  fact  that  the  water 
flows  along  the  under  side  of  the  pans,  or  the  lime  formation  thereon, 
and  thus  comes  in  direct  contact  with  the  exhaust-steam,  no  matter 
how  thick  the  lime  formation  may  be  on  the  pans.  The  apparatus 
is  provided  with  a  large  oil-catcher,  located  in  the  rear,  and  through 
which  all  the  steam  passes  and  is  purified  before  entering  the  heater. 


92 


HEAT-ECONOMY  OF  THE  FEED-WATER 


A  float  is  provided  which  operates  a  balanced  valve  for  the  regulation 
of  the  feed-water.  The  entire  front  head  is  easily  removed  and 
swung  to  one  side  by  a  crane  provided  for  this  purpose,  so  that  the 
pans  may  be  readily  removed.  As  the  pans  contain  all  of  the  lime 
and  other  solids  formed  in  the  heater,  the  entire  work  of  cleaning  is 
performed  outside  of  the  heater. 


THE     GREEN     F U E L - E C O N O M I  Z  E  R 

This  apparatus  consists  of  a  stack  of  tubes  arranged  vertically  in 
the  flue  leading  from  the  boiler  to  the  chimney  (as  illustrated  in  Fig. 
79),  and  is  designed  to  utilize  the  waste  heat  in  the  gases  passing  off 
from  the  furnace.  This  is  accomplished  by  absorbing  the  low-tem- 


FIG.  79. — Green  fuel-economizer. 

perature  heat  of  the  gases  in  heating  the  feed-water,  which  is  pumped 
through  the  economizer  before  entering  the  boiler.  The  waste  gases 
are  led  to  the  economizer  by  the  ordinary  flue  from  the  boilers  to  the 
chimney. 

The  feed- water  is  forced  into  the  economizer  by  the  boiler  feed- 
pump, or  an  injector,  at  the  lower  branch  pipe  nearest  the  point  of 
exit  of  the  gases,  and  emerges  from  the  economizer  at  the  upper 
branch  pipe  nearest  the  point  where  the  gases  enter. 


HEAT-ECONOMY  OF  THE  FEED-WATER  93 

Each  tube  is  provided  with  a  geared  scraper,  which  travels  con- 
tinuously up  and  down  the  tubes  at  a  low  rate  of  speed,  the  object 
being  to  keep  the  external  surface  clean  and  free  from  soot. 

The  mechanism  for  working  the  scrapers  is  placed  on  the  top  of 
the  economizer,  outside  the  chamber,  and  is  very  simple  and  effective; 
the  motive  power  is  supplied  either  by  a  belt  from  some  convenient 
shaft  or  by  a  small  independent  engine  or  motor.  The  power  required 
for  operating  the  gearing  is  very  small. 

The  apparatus  is  fitted  with  blowoff-  and  safety-valves,  and  a 
space  is  provided  at  the  bottom  of  the  chamber  for  the  collection  of 
the  soot  removed  by  the  scrapers. 

The  scrapers  are  three  in  number  and  encircle  the  pipes  with  the 
joints  overlapping  one  another.  They  have  thin,  beveled  cutting- 
edges  which  entirely  remove  any  accumulation  of  soot.  Under 
conditions  where  a  forced  circulation  may  be  an  advantage,  circu- 
lating blow-off  manifolds  are  introduced.  By  means  of  these  mani- 
folds any  portion  or  the  whole  of  the  economizer  can  be  made  to  cir- 
culate, and  at  the  same  time  every  section  can  be  thoroughly  blown 
off.  As  the  economizer  should  be  blown  off  for  a  few  moments  at 
least  once  a  day,  the  valves  are  connected  together  by  a  long  lever, 
which  makes  the  operation  very  simple  and  takes  the  least  possible 
time  to  operate. 


CHAPTER    VII 

THE   INJECTOR   AND   THE   STEAM-PUMP 

THE  injector  and  its  theory  were  matters  of  much  discussion 
during  the  early  years  of  its  use,  and  its  final  solution  has  been  mathe- 
matically demonstrated  as  the  elimination  of  the  volume  of  the 
steam-jet  at  a  high  velocity  by  the  instantaneous  absorption  of  its 
latent  heat  in  contact  with  the  incoming  water,  thus  imparting  its 
velocity  momentum  to  the  water  around  it,  by  which  interchange  of 
temperatures  the  volume  of  the  steam  is  reduced  to  the  volume  of 
its  water-base.  By  this  action  its  proportionate  velocity  is  imparted 
to  the  incoming  annular  water-jet,  which  becomes  a  solid  water-jet 
at  the  end  of  the  combining-nozle,  the  momentum  of  which  is  far 
greater  than  is  required  to  overcome  the  resistance  of  the  boiler- 
pressure,  and  the  jet  crosses  a  starting  relief-space  and  enters  the 
delivery-nozle,  opening  by  its  force  the  boiler  check-valve. 

The  formulas  representing  the  action  of  an  injector  are  as  follows: 
For  the  velocity  of  the  injection  at  the  exit  of  the  combining-nozle 
we  have,  V  =  12.19  |/p  in  feet  per  second,  in  which  p  =  the  gauge-press- 
ure. The  volume  of  water  and  condensed  steam  passing  the  nozle 
of  the  combining-tube,  per  second,  will  be  0.016  (W  +  W0);  and  if  A 
be  the  area  and  W  the  weight  of  the  steam,  and  Wo  the  weight  of  the 

.       .        A=0.016  (W+Wp)   . 
water,  then — * ;  in  which  V  =  velocity,  as  found  above. 

The  velocity  of  the  steam  may  be  found  from  the  formula : 
V  =  23.2687  A/ p  v  (l  -  ^0.1189 V  in  which  p  =  absolute   initial 

pressure,  v  =  volume  of  steam  at  initial  pressure,  and  p2  =  pressure  in 
the  chamber  between  the  nozles — generally  atmospheric  pressure. 

Table  XV  is  an  approximate  service  of  a  simple  injector,  equal 
to  the  delivery  of  about  1  pound  of  water  per  second  at  a  tempera- 
ture of  160°  F.  from  feed-supply  at  60°  F. 
94 


THE  INJECTOR  AND  THE  STEAM-PUMP 


95 


TABLE  XV. — GAUGE-PRESSURES,  NOZLE-DIAMETERS,  AND  VELOCITIES  OF  STEAM  AND 
WATER  AND  THEIR  RATIOS. 


Gauge- 
pressure, 
pounds. 

Diameter 
steam- 
nozle, 
inches. 

Diameter 
water- 
nozle, 
inches. 

Velocity 
steam, 
feet  per 
second. 

Velocity 
steam  and 
water,  feet 
per 
second. 

Ratio  of 
velocity 
steam  to 
water. 

Ratio  of 
weight, 
water  to 
steam. 

Ratio  of 
volume, 
steam  to 
water. 

30 

0.28 

0.21 

2007.9 

66.7 

30. 

10.3 

55.9 

40 

0.24 

0.20 

2178.8 

77.1 

28.    - 

10.3 

46.2 

50 

0.22 

0.19 

2213.5 

86.2 

25. 

10.4 

39.4 

60 

0.20 

0.18 

2428.8 

94.4 

25. 

10.5 

34.4 

70 

0.18 

0.178 

2522.3 

101.2 

25. 

10.5 

30.4 

80 

0.17 

0.172 

2554.1 

108.0 

24. 

10.5 

27.6 

90 

0.167 

0.166 

2590.6 

115.6 

22. 

10.5 

25.2 

100 

0.159 

0.160 

2735.8 

121.8 

22. 

10.5 

22.8 

120 

0.142 

0.154 

2842.7 

133.5 

21. 

10.6 

19.6 

140 

0.133 

0.149 

2922.3 

144.2 

20. 

10.6 

17.2 

160 

0.127 

0.143 

2999.7 

154.2 

19. 

10.6 

15.3 

CHECK  VALVE- 


Under  ordinary  conditions  an  injector  will  feed  about  12  pounds 
of  water  to  a  boiler  per  pound  of  steam,  or  13  pounds  including  its  own 
weight. 

The  limit  of  the  feed- water  temperature  for  an  injector  is  about 
110°  F.,  so  that  open  feed-water  heaters  cannot  supply  the  water; 
but  injectors  can  feed  boilers  through  closed  heaters  to  advantage, 
with  possibilities  of  raising  the  temperature  of  the  feed- water  to  near 
212°  F. 

Of  the  many  models  of  injectors  on  the  market,  the  tandem  and 
double  combining-tube  models  are  taking  the  lead  for  efficiency  and 
reliability.  Following  are  illus- 

arc  AU  TO  noil  FB 

trated  some  of  the  various 
models  in  section,  showing 
their  details  of  construction: 

The  Penberthy  injector,  Fig. 
80,  special  model,  has  three 
fixed  nozle-tubes  in  line.  The 
opening  of  a  detached  valve 
gives  steam  to  the  chamber  E 
through  the  annular  orifice  be-  FlG  80._Periberthy  injector, 

tween  the  combining-  and  re- 

ceiving-nozles  at  F,  and  by  its  pressure  opens  the  relief  check- 
valves  C  and  D.  When  the  water-current  is  established,  the  pressure 
in  the  chamber  next  to  the  boiler  check-valve  closes  the  check-valve 


96 


THE  INJECTOR  AND  THE  STEAM-PUMP 


D,  which  by  the  contact  of  its  wings  with  the  check-valve  C  closes  it, 
and  the  full  pressure  opens  the  boiler  check-valve. 

The  Little  Giant,  Fig.  81,  is  an  adjustable  injector  in  which  two  of 
its  three  tubes  are  fixed.  The  combining- tube  is  movable  for  adjust- 
ment by  the  lever-handle,  which  by  drawing  the  combining-tube 

toward  the  steam-nozle  regu- 
lates the  flow  of  water,  and  the 
steam  is  regulated  by  a  de- 
tached valve.  The  relief  check- 
valve  C  automatically  closes  on 
the  establishment  of  the  water- 
current. 


FIG.  81. — Little  Giant  injector. 


The  Lunkenheimer  injector, 
Fig.  82,  has  four  fixed  nozle- 
tubes,  with  all  the  valves  required  for  operating  it  attached  to  the 
injector.  The  steam-regulating  valve  is  adjusted  by  a  lever  as  shown; 
D  is  the  stop-check  to  the  overflow,  which  is  carried  around  the  body 
of  the  injector  to  the  nozle  below.  In  starting,  the  pressure,  by  the 
escape  of  steam  at  the  annular  orifice  into  the  chamber  E,  opens  the 
relief-check  C.  When  the  water-current  is  established,  the  overflow- 
check  at  D  is  closed,  and  the  pressure  from  the  nozle  of  the  second 
section  of  the  combining-tube 
in  the  chamber  S  closes  the 
check-valve  C,  and  the  water 
and  steam  pass  this  gap  in  a 
solid  stream. 

Of  the  tandem  nozle-injec- 
tors  there  are  a  great  variety 
of  models  on  the  market,  each 
having  its  own  peculiar  feat- 
ures. The  double- tube  injec- 
tors, although  seemingly  some- 
what more  complex  in  their  construction,  are  claimed  to  deliver  the 
feed-water  at  a  higher  temperature  by  the  fact  that  the  water  passes 
successively  through  two  combining-nozles. 

As  an  example  of  this  class  we  illustrate  in  section,  in  Fig.  83,  the 
Metropolitan  double-tube  injector. 


FIG.  82. — Lunkenheimer  injector. 


THE  INJECTOR  AND  THE  STEAM-PUMP 


97 


The  steam  is  turned  on  from  a  separate  valve;  the  first  movement 
of  the  handle  opens  the  first  section  of  a  double-beat  valve  at  b,  and 
gives  the  steam  to  the  lifting- 
nozle  A;  the  overflow  passing 
freely  through  the  check- valve 
€  and  the  open  valve  at  D.  A 
further  movement  of  the  handle 
opens  the  second  section  of  the 
double-beat  valve  B,  and  closes 
the  overflow-valve  D,  when  the 
flow  of  warm  water  from  the  first 
tube,  M,  flows  into  the  chamber  FIG.  83.— Metropolitan  injector. 

F,  and  to  the  second  tube,  and 

through  the  chamber  G  to  the  boiler.     The  pressure  in  G  at  the  mo- 
ment of  discharge  of  the  second  tube  closes  the  overflow-valve  C. 

The  Korting  injector,  Fig.  84,  is  of  the  double-tube  variety,  with 
an  automatic  movement  by  which  the  difference  in  area  of  the  valve- 
disks  at  A  and  B  allows  the  balance-lever  to  open  the  lifting-nozle 
first,  and  by  a  further  movement  of  the  handle  opens  the  force- 
nozle  B.  The  overflow  is  self-adjusting  for  both  nozles. 

The  real  efficiency  in  the  injector,  and  its  economy  in  saving  part 
of  the  heat  lost  by  the  exhaust,  are  found  in  the  exhaust-injector 


— >•  TO  BOILER 


FIG.  84. — Korting  injector. 


FIG.  85. — Exhaust-injector. 


(shown  in  Fig.  85)  of  the  triple-tube  model,  in  which  the  centre  or 
combining-tube  has  a  hinged  section  which  opens  automatically  by 


98  THE  INJECTOR  AND  THE  STEAM-PUMP 

the  incoming  exhaust,  and  allows  a  free  flow  to  draw  the  water  into 
the  nozle«»and  through  the  overflow.  When  the  water-current  is 
established  the  hinged  section  of  the  combining-tube  automatically 
closes,  and  the  injector  operates  the  same  as  others  for  feeding  a 
boiler.  The  portion  of  the  exhaust  not  used  by  the  injector  may 
pass  through  a  heater  which  the  injector  feeds,  thus  increasing  the 
feed-water  temperature. 

The  efficiency  of  the  injector  as  a  heat  device  is  claimed  to  be 
theoretically  perfect,  as  it  returns  all  the  heat  it  receives  from  the 
boiler  save  the  radiation  and  the  small  losses  in  starting;  but  as  a 
pump  for  elevating  water  its  efficiency  is  very  low  in  comparison  with 
the  steam-pump,  being  about  one-fifth  as  efficient.  The  work  of  forcing 
water  into  a  boiler,  say  at  80  pounds  pressure,  in  the  proportion  of  13 
pounds  of  water  to  1  pound  of  steam,  as  shown  in  Table  XV,  is,  144  X 
80X13X0.016  =  2,396  foot-pounds.  One  pound  of  steam  in  the 
direct-acting  steam-pump  will,  at  80  pounds  boiler-pressure,  do  the 
actual  work  of  10,000  foot-pounds,  or  over  four  times  as  much  as  an 
injector.  A  pump  feeding  a  boiler  at  80  pounds  pressure  which 
generates  8J  pounds  of  steam  per  pound  of  coal  consumes  about  2 
per  cent,  of  the  fuel. 

THE     STEAM-PUMP     AND     ITS     WORK 

The  power  required  to  force  water  against  a  given  pressure  or 
height  must  include  in  its  resistance  the  height  of  the  draught  or 
suction  and  the  friction  of  the  pump  as  a  machine,  as  the  three  static 
elements  against  which  the  pump  must  work;  and  also  the  element 
of  action  to  keep  the  pump  moving  at  the  required  speed.  The 
friction  and  action  elements  of  pump-work,  especially  in  small  pumps, 
may  be  as  much  as  60  per  cent,  greater  than  the  total  static  force  of 
the  pump's  work. 

In  pumps  used  for  boiler-feeding  with  pressure-supply,  the  usual 
ratio  of  diameter  of  steam-cylinder  to  water-cylinder  is  from  1.20  to 
1.25;  but  where  extreme  suction-lift  has  to  be  overcome,  a  ratio  of 
1.30  is  a  safer  assurance  of  proper  action,  and  in  such  cases  only 
pumps  with  very  small  clearance  can  be  relied  upon. 

The  formulas  for  the  balance  of  pressure  and  areas  in  steam- 
pumps,  to  which  should  be  added  the  necessary  steam-pressure  for 
actuating  the  pumps,  are: 


THE  INJECTOR  AND  THE  STEAM-PUMP 


99 


water-pressure 


area  steam  -  cylinder  -=-  area  water  -  cylinder 
area  water-cylinder  X  water-pressure 


=  steam-pressure. 


area  steam-cylinder 
water-pressure  area  steam-cylinder 
steam-pressure  area  water-cylinder 
area  steam-cylinder  X  steam-pressure 

water-pressure 
area  steam-cylinder  X  steam-pressure 


=  steam-pressure. 


=  area  water-cylinder. 


water-pressure. 


area  water-cylinder 

For  obtaining  the  actual  horse-power  that  is  required  to  operate 
a  pump,  we  have  weight  of  water  in  pounds  per  minute  X  height  (or 
pressure  X  2.3)  -*•  33,000  =  horse-power. 

The  decreasing  pressure  of  the  atmosphere  at  a  height  above  sea- 
level  materially  affects  the  suction-lift  of  a  pump.  Assuming  that 
the  practical  lift  of  a  pump  at  sea-level  is  25  feet,  the  following  table 
shows  the  comparative  height,  pressures  in  pounds,  and  equivalent 
head  of  water  in  feet,  and  the  corresponding  practical  lift  of  pumps : 

TABLE  XVI. — HEIGHT  AND  ATMOSPHERIC  PRESSURE,  WITH  EQUIVALENT  HEAD  OP 

WATER  AND  PUMP-LIFT. 


ALTITUDE  ABOVE  SEA-LEVEL. 

Pressure,  pounds 
per  square  inch. 

Equivalent  head 
of  water,  feet. 

Practical  suction- 
lift  in  feet. 

Ats 
irr 

1 
If 

? 

ea-level  

14.70 
14.02 
13.33 
12.66    . 
12.02 
11.42 
10.88 
9.88 

33.95 
32.38 
30.79 
29.24 
27.76 
26.38 
25.13 
22.82 

25. 
24. 
23. 
21. 
20. 
19. 
18. 
17. 

iile=   1,320  f( 
=  2,640 
=  3,960 
-  5,280 
=--  6,600 
=  7,920 
=  10,560 

?et 

In  the  ordinary  practice  of  piping  pumps  for  feeding  boilers  the 
friction  of  the  water  in  the  pipes  is  not  considered;  but  sometimes 
long  suction-pipes  are  required,  when  the  friction  may  be  serious,  or 
an  obstacle  to  high  lifts.  Five  hundred  to  1,000  feet  are  feasible  dis- 
tances for  pump-suction  with  an  ample  air-chamber  on  the  suction-pipe 
near  the  pump  and  with  lifts  as  in  the  table,  less  the  friction-head  for 
pipe  and  fittings. 


100 


THE   INJECTOR   AND   THE   STEAM-PUMP 


L    4V2  +  5V  —  9 
The  formula  for  straight  pipe  is :  -  X -  =  friction-head  in  feet. 

L  =  length  in  feet;  d  =  diameter  in  inches;  V  =  velocity  of  the  water 
in  feet  per  second.  An  elbow  is  equal  to  60  diameters,  and  a  globe- 
valve  equal  to  90  diameters,  of  the  pipe,  and  should  be  added  to  the 
length  of  the  pipe. 

Of  the  many  models  of  boiler-pumps,  we  can  illustrate  only  a 
few  of  those  having  special  features. 

In  Fig.  86  is  shown  a  sectional  view  of  the  Knowles  steam-pump. 
Freedom  from  stoppage  on  a  dead  centre  of  the  valve-movement  is 


FIG.  86. — Knowles  single  pump. 

secured  by  the  use  of  the  auxiliary  piston  A,  which  works  in  the  steam- 
chest  and  drives  the  main  slide-valve  M.  This  main  valve  is  of  the 
B  form  and  moves  on  a  flat  seat;  it  has  on  top  a  stem  which  fits  into 
a  recess  in  the  piston  A.  The  chest-piston  A  has  a  slight  rotation 
from  the  curved  rocker-bar  R,  which  alternately  covers  and  uncovers 


FIG.  87. — Knowles  duplex  pump. 

small  ports,  S,  S,  which  enter  the  cylinder  at  each  end  near  the  head. 
The  steam-piston  runs  over  the  main  ports,  and  by  its  cushion  operates 
the  piston-valve  and  the  main  valve. 


THE  INJECTOR  AND  THE  STEAM-PUMP 


101 


The  Knowles  duplex  pump  is  shown  in  section  in  Fig.  87.  This 
pump  has  a  double  set  of  steam-ports  which  produce  a  cushion  at 
each  piston-stroke  by  covering 
the  inside  ports  alternately;  the 
plain  D  valve  making  the  clos- 
ure by  its  movement.  A  rocker- 
arm  linked  to  the  piston-rod  of 
each  side  of  the  pump  operates 
the  opposite  valve. 


The  Worthington  duplex 
pump,  Fig.  88,  has  the  same 
valve-movement  and  cushion- 
ing-ports  as  above  described; 


FIG.  88. — Worthington  duplex  pump. 


but  the  water-piston  is  of  the  plunger  form,  with  the  inlet-valves  at 
the  bottom  of  the  cylinder. 

Fig.  89  shows  the  vacuum-pump  and  jet-condenser,  and  Figs. 
90  and  91  show  the  details  of  the  valve-gear  used  on  the  Deane  single- 
cylinder  steam-pumps.  The  main  valve  is  operated  by  a  small  piston 

called  the  valve-piston.  The 
ears  on  the  main  valve  fit 
tightly  in  a  slot  cut  in  the 
valve-piston,  so  that  when 
the  valve-piston  moves  in 
either  direction  it  carries  the 
main  valve  with  it. 

The  valve-piston  is  fitted 
to  and  slides  in  a  cylindrical 
bore  in  the  valve-chest,  and 
is  actuated  by  steam  ad- 
mitted to  the  opposite  ends 
of  the  chest.  The  admission 
and  exhaust  of  this  steam 
are  controlled  by  a  second- 
ary valve,  which  admits  or 
exhausts  the  steam  for  the  valve-piston  through  the  small  ports  at 
the  sides  of  the  cylinder  and  chest.  The  secondary  valve  derives  its 
motion,  through  the  valve-rod,  tappets,  and  links  shown,  from  the 


FIG.  89. — Deane  vacuum-pump  with  jet- 
condenser. 


102 


THE  INJECTOR  AND  THE  STEAM-PUMP 


main  piston-rod.     Thus,  the  movement  of  the  secondary  valve,  and 
hence  the  valve-piston  and  main  valve,  are  controlled  by  the  main 


FIG.  90. — Valve-gear,  Deane  pump. 

piston.     The  valve-piston,  it  will  be  noticed,  has  a  steam-jacket  which 
insures  equal  expansion  of  the  parts  and  prevents  binding. 

The  piston-rod  arm  is  fastened  to  the  piston-rod,  and  through  the 
connection  of  lever  and  links  its  motion  causes  the  tappet-block  to 
slide  back  and  forth  on  the  valve-rod  between  the  two  tappets.  These 
tappets  are  keyed  to  the  valve-rod  so  that  when  the  tappet-block 
strikes  either  tappet  it  carries  with  it  the  valve-rod  and  secondary 
valve.  When  the  piston  moving  in  the  direction  indicated  by  the  arrow 
has  come  almost  to  the  end  of  the  stroke,  the  tappet-block  monies  in 
contact  with  the  left-hand  tappet,  and  the  further  movement  of  the 
piston  throws  the  secondary  valve  to  the  left  until  the  edge  A,  Fig.  91, 


FIG.  91. — Valve-chest  and  auxiliary  valve. 

uncovers  the  small  port  S.  The  port  S,  together  with  passages  in 
the  cylinder-  and  valve-chest,  allows  the  steam  to  fill  the  space  between 
the  right-hand  end  of  the  valve-piston  and  the  valve-chest  head, 


THE  INJECTOR  AND  THE  STEAM-PUMP 


103 


and  exerts  a  pressure  forcing  the  valve-piston  in  the  direction  indicated 
by  the  arrow.  In  the  illustration,  Fig.  90,  the  valve-piston  has  already 
moved  part  of  the  way,  carrying  the  main  valve  with  it  far  enough  to 
partially  open  the  steam-port  which  admits  steam  to  the  right-hand 
end  of  the  cylinder,  and  the  main  piston  is  ready  to  start  back  in  the 
other  direction.  The  port  E  and  the  chamber  F.in  the  secondary 
valve,  as  shown  in  Fig.  91,  provide  for  the  exhaust  of  steam  from 
behind  the  left-hand  end  of  the  valve-piston  in  the  same  manner  and 
at  the  same  time  that  steam  is  admitted  behind  the  right-hand  end. 
The  location  of  the  exhaust-ports  in  the  chest  is  such  as  to  allow  for 
proper  cushioning  of  the  valve-piston  to  prevent  its  striking  the  heads. 
The  small  ports  on  the 
other  side  of  the  steam- 
cylinder  control  the  mo- 
tion of  the  valve  in  the 
other  direction,  and  act  in 
exactly  the  same  manner. 
In  case  the  steam-pressure 
should  for  any  reason  fail 
to  start  the  valve-piston 
at  the  proper  time  there 
is  a  lug,  B,  Fig.  90,  pro- 
vided on  the  valve-rod 
which  comes  in  contact 
with  the  valve-piston  and 
brings  to  bear  the  whole 
power  of  the  steam-cylin- 
der to  start  it.  It  is  readily  seen  that  the  correct  timing  of  the 
valve-movements  is  independent  of  the  position  of  the  tappets.  If 
they  are  too  near  together  the  valve  will  be  thrown  too  soon,  and 
thus  the  stroke  of  the  pump  will  be  shortened;  while,  on  the  other 
hand,  if  they  are  too  far  apart,  the  pump  will  complete  its  stroke 
without  moving  the  valves. 

In  the  Cameron  pump  the  plunger  is  reversed  by  means  of  two 
plain  tappet-valves,  shown  in  Fig.  92,  and  the  entire  mechanism  thus 
consists  of  four  pieces  only,  all  working  in  direct  line  with  the  main 
piston.  It  is  simple  and  without  delicate  parts. 

A  is  the  steam-cylinder;  C,  the  piston;  L,  the  steam-chest;  F,  the 


FIG.  92. — Sectional  view  of  Cameron  pump. 


104  THE   INJECTOR  AND  THE  STEAM-PUMP 

chest-plunger,  the  right-hand  end  of  which  is  shown  in  section;  G,  the 
slide-valve;  H,  a  lever,  by  means  of  which  the  steam-chest  plunger  F 
may  be  reversed  by  hand  when  expedient;  I,  I  are  reversing-valves; 
K,  K  are  the  reversing-valve  chamber-bonnets,  and  E,  E  are  exhaust- 
ports  leading  from  the  ends  of  the  steam-chest  direct  to  the  main 
exhaust  by  means  of  passages,  M,  M,  which  lead  directly  thereto, 
although  the  connection  is  not  shown,  being  cut  away  in  the  sectional 
view,  and  closed  by  the  reversing-valves  I,  I. 

The  piston  C  is  driven  by  steam  admitted  under  the  slide-valve  G, 
which  as  it  is  shifted  backward  and  forward  alternately  connects 
opposite  ends  of  the  cylinder  A  with  the  live-steam  pipe  and  exhaust. 
This  slide-valve  G  is  shifted  by  the  auxiliary  plunger  F;  F  is  hollow 
at  the  ends,  which  are  filled  with  steam,  and  this,  issuing  through  a 
hole  in  each  end,  fills  the  spaces  between  it  and  the  heads  of  the  steam- 
chest  in  which  it  works.  Pressure  being  equal  at  each  end,  this  plunger 
F,  under  ordinary  conditions,  is  balanced  and  motionless;  but  when  the 
main  piston  C  has  travelled  far  enough  to  the  left  to  strike  and  open 
the  reversing-valve  I,  the  steam  exhausts  through  the  port  E  from 
behind  that  end  of  the  plunger  F,  which  immediately  shifts  accordingly 
and  carries  with  it  the  slide-valve  G,  thus  reversing  the  pump.  No 
matter  how  fast  the  piston  may  be  travelling,  it  must  instantly  reverse 
on  touching  the  valve  I.  In  its  movement  the  plunger  F  acts  as  a 
slide-valve  to  close  the  port  E,  and  is  cushioned  on  the  confined  steam 
between  the  ports  and  steam-chest  cover.  The  reversing-valves  I,  I 
are  closed,  as  soon  as  the  piston  C  leaves  them,  by  a  constant  pressure 
of  steam  behind  them,  direct  from  the  steam-chest  through  the  ports 
N,  N,  shown  by  the  dotted  lines. 

In  the  McGowan  single-cylinder  pump  the  main  valve  is  of  the  B 
form  and  is  driven  by  a  chest-piston  or  valve-driver,  as  shown  in  Fig. 
93.  Steam  is  alternately  admitted  through  one  of  the  cavities  in  the 
valve  and  is  released  through  the  other,  the  central  port  in  the  valve- 
seat  admitting  the  live  steam.  Immediately  below  the  ends  of  the 
steam-chest  are  two  tappet-valves,  which  normally  cover  the  auxiliary 
ports  (shown  by  dotted  lines),  leading  to  the  ends  of  the  steam-chest 
and  connecting  the  latter  with  the  main  exhaust-ports.  The  tappet- 
valves  are  raised  by  means  of  levers,  the  ends  of  which  project 
downward  and  into  the  cylinder,  so  that  when  the  piston  nears 


THE  INJECTOR  AND  THE  STEAM-PUMP 


105 


the  ends  of  the  stroke  it  comes  into  contact  with  the  levers  and 
raises  them  slightly,  the  movement  being  merely  sufficient  to  unseat 
the  tappet-valves. 

The  tappet-valve  levers  are  pivoted  on  a  pin  in  a  recess  near  the 
main  ports,  the  latter  being  indicated  by  dotted  lines. 

When  the  piston  reaches  the  end  of  the  stroke,  one  of  the  tappet- 
levers  is  raised  slightly  and  the  corresponding  valve  is  raised  from  its 
seat.  This  opens  the  port  leading  from  the  end  of  the  steam-chest  to 
the  main  exhaust-port 
and  permits  steam  to 
escape  into  the  latter. 
The  pressure  is  thus  les- 
sened on  one  end  of  the 
chest-piston  or  valve- 
driver,  and  the  steam 
pressing  on  the  opposite 
end  forces  the  valve- 
driver  to  the  opposite 
end  of  its  stroke,  thus 
reversing  the  distribu- 
tion of  steam  to  the 
cylinder  and  starting  the 
piston  on  the  return 
stroke.  The  chest-piston 
is  caused  to  move  back 
and  forth  by  live  steam, 
the  ends  of  the  steam- 
chest  being  filled  with 
steam  at  initial  press- 
ure. Permitting  steam  to  escape  from  one  end  of  the  steam-chest 
causes  a  difference  of  pressure  on  the  two  ends  of  the  chest-piston, 
which  difference  represents  the  propelling  force  that  moves  the  main 
valve.  The  tappet-valves  have  a  very  slight  lift,  so  that  they  operate 
without  shock  or  noise  and  with  the  minimum  of  wear.  The  main 
valve  is  connected  with  the  chest-piston  or  valve-driver  in  such  a 
manner  that  all  lost  motion  and  wear  is  taken  up  automatically. 

A  short  rocker-shaft,  extending  through  the  steam-chest  and  at 
right  angles  to  the  valve-travel,  carries  a  toe  which  depends  in  a  slot  in 


FIG.  93. — Sectional  view  of  steam-end,  McGowan 
pump. 


106 


THE  INJECTOR  AND  THE  STEAM-PUMP 


the  top  of  the  chest-piston,  so  that  in  event  the  latter  should  chance 
to  stop  with  the  ports  closed,  the  valve  can  be  moved  by  hand  without 
disconnecting  any  part  of  the  pump. 


THE    GUILD    &    GARRISON    PUMP 

The  steam-chest  of  this  pump  is  a  rectangular  chamber,  provided 
at  each  end  with  suitable  cylinders  to  receive  the  pistons  of  the  valve- 
driver  E,  Fig.  94.  At  the  side  of  the  valve-driver  E,  and  in  the 

steam-chest,  is  an  auxil- 
iary slide-valve,  G,  Figs. 
94  and  95,  which  admits 
and  releases  the  steam 
from  the  ends  of  the 
valve-driver.  The  valve- 
driver  E  has  two  slots 
at  the  centre,  the  lower 
one  receiving  the  lug  on 
the  back  of  the  main 
valve,  and  the  upper  one 
the  toe  on  the  rocker- 
shaft  D.  The  rocker- 
shaft  has  two  toes,  the 
larger  one  engaging  with 


the  valve-driver,  and  the 
smaller  one  with  the 
auxiliary  slide-valve  G, 
as  shown  in  Fig.  96. 
Both  the  main  and  the 


FIG.  94. — Steam-cylinder,  Guild  &  Garrison  pump. 


auxiliary  valves  are  plain  slide-valves,  so  fitted  as  to  take  up  wear 
automatically.  The  pendulum-lever  J,  Fig.  96,  causes  the  shaft  D  to 
rotate,  and  by  means  of  the  toes  previously  referred  to  the  valves  are 
caused  to  move  in  unison. 

The  auxiliary  valve  G  is  in  every  respect  similar  to  the  slide-valve 
of  an  engine,  and  admits  and  releases  the  steam  to  and  from  the  ends 
of  the  valve-driver. 

The  operation  of  the  valves  is  as  follows :  The  piston  being  at  the 
end  of  the  stroke,  steam  is  admitted  by  the  main  valve,  and  the  piston 


THE  INJECTOR  AND  THE  STEAM-PUMP 


107 


moves  toward  the  opposite  end  of  the  stroke.  The  two  valves  are 
also  moved  in  the  same  direction  by  means  of  the  rocker-shaft  and  the 
toes.  This  movement  is  con- 
tinued until  the  piston  has 
nearly  completed  the  stroke, 
when  the  auxiliary  valve  opens 
one  of  the  small  ports  leading 
to  the  end  of  the  valve-driver, 
thus  admitting  steam  at  one 
end  and  releasing  it  from  the 
other,  which  causes  the  valve- 
driver  to  move  from  one  end  „  , 

FIG.  95. — Sectional  view  of  valve-chest, 

of  the  steam-chest  to  the  other,  Guild  &  Garrison  pump. 

which    movement    also    shifts 

the  position  of  the  main  valve  and  reverses  the  motion  of  the  main 

piston.  The  valve-driver  is  moved  the  greater  part  of  the  distance  by 

means  of  the  toe  on  the 
rocker-shaft,  the  stroke 
or  travel  of  the  driver 
being  completed,  thus  re- 
versing the  steam-distri- 
bution by  steam-press- 
ure, which  brings  the 


FIG.  96. — Auxiliary  valve,  Guild  &  Garrison  pump. 


opposite  end  of  the  slot 
in  the  driver  in  position 
to  be  again  engaged  by  the  toe  on  the  rocker-shaft  for  the  return  stroke. 


In  the  Blake  single-cylinder  pump  the  main  valve,  which  controls 
the  admission  of  steam 
to  and  the  escape  of 
steam  from  the  main 
cylinder,  is  divided  into 
two  parts,  one  of  which, 
G,  Figs.  98  and  99,  slides 
upon  a  seat  on  the  main 


FIG.  97. — Plan  of  Blake  pump-valve. 


cylinder,  and  at  the  same 

time  affords  a  seat  for 

the  other  part,  D,  which  slides  upon  the  upper  face  of  G.    As  shown 

in  the  illustrations,  D  is  at  the  left-hand  end  of  its  stroke,  and  G  at  the 


108 


THE  INJECTOR  AND  THE  STEAM-PUMP 


FIG.  98. — Section  of  Blake  pump. 


opposite  or  right-hand  end  of  its  stroke.  Steam  from  the  steam- 
chest  J  is  therefore  entering  the  right-hand  end  of  the  main  cylinder 
through  the  ports  E  and  H,  and  the  exhaust  is  escaping  through  the 
ports  HI,  EI,  K,  and  M,  which  causes  the  main  piston  A  to  move  from 
right  to  left.  When  the  piston  has  nearly  reached  the  left-hand  end 

of  the  cylinder  the  valve- 
motion  moves  the  valve- 
rod  P,  and  thus  causes  G, 
together  with  its  supple- 
mental valves  R  and  S, 
Si,  Fig.  99  (which  form, 
with  G,  one  casting),  to  be 
moved  from  right  to  left. 
This  causes  steam  to  be 
admitted  to  the  left-hand 
end  of  the  supplemental 
cylinder,  whereby  the  pis- 
ton B  will  be  forced  to- 
ward the  right,  carrying 
D  with  it  to  the  opposite  or  right-hand  end  of  its  stroke;  for  the  move- 
ment of  S  closes  N,  the  steam-port  leading  to  the  right-hand  end,  and 
the  movement  of  Si  opens  NI,  the  steam-port  leading  to  the  opposite 
or  left-hand  end,  at  the  same  time  the  movement  of  V  opens  the  right- 
hand  end  of  this  cylinder  to  the  exhaust,  through  the  exhaust-ports 
X  and  Z.  The  parts  G  and  D  now  have  positions  opposite  to  those 
shown  in  the  cuts,  and  steam  is  therefore  entering  the  main  cylin- 
der through  the  ports  EI  and 
HI,  and  escaping  through  the 
ports  H,  E,  K;  and  M,  which 
will  cause  the  main  piston  A 
to  move  in  the  opposite  direc- 
tion, or  from  left  to  right,  and 
operations  similar  to  those  al- 
ready described  will  follow  when  the  piston  approaches  the  right- 
hand  end  of  the  cylinder.  By  this  simple  arrangement  the  pump  is 
rendered  positive  in  action ;  that  is,  it  will  start  and  continue  working 
the  moment  steam. is  admitted  to  the  steam-chest. 

The  main  piston  A  cannot  strike  the  heads  of  the  cylinder,  for 


FIG.  99. — Main  valve  and  rider. 


THE  INJECTOR  AND  THE  STEAM-PUMP 


109 


r 

FIG.  100. — Dean  duplex  pump. 


the  main  valve  has  lead ;  or,  in  other  words,  steam  is  always  admitted 
in  front  of  the  piston  just  before  it  reaches  either  end  of  the  cylinder, 
even  though  the  supplemental  piston  B  be  tardy  in  its  action  and 
remain  with  D  at  that  end  toward  which  the  piston  A  is  moving, 
for  G  would  be  moved  far  enough  to  open  the  steam-port  leading  to 
the  main  cylinder,  since  the  possible  travel  of  G  is  greater  than  that 
of  D. 

The  supplemental  piston  B  cannot  strike  the  heads  of  the  smaller 
cylinder,  for  in  its  alternate  passage  beyond  the  exhaust-ports  X 
and  Xi  it  cushions  on  the 
vapor  entrapped  in  the  ends 
of  the  cylinder. 

The  Dean  duplex  pump, 
Fig.  100,  varies  but  very  little 
in  its  valve-gear  from  the 
Worthington  and  Knowles 
pumps  of  the  duplex  model, 
while  its  water-cylinder  and  valves  are  the  same  as  the  Knowles  pat- 
tern. 

These  sectional  views  represent  the  valve-gear  and  general  action 
of  a  majority  of  the  boiler  feed-pumps  on  the  market,  and  a  further 
illustration  may  not  be  desirable. 

The  basket-strainer,  Fig.  101,  is  a  most  desirable  appendage  at 
or  near  the  entering  end  of  a  suction-pipe  drawing  water  from  a  river 

or  pond,  and  consists  of  a  perforated 
plate  or  frame  covered  with  wire 
cloth,  slid  into  a  cylinder,  as  shown, 
with  a  cover  and  yoke  which  allow  of 
cleaning  and  of  removal  of  fish  and 
floating  vegetation  (eels  often  give 
much  trouble  in  suction-pipes)  with- 
out having  to  take  up  a  submerged 
strainer. 

Pumps  should  go  slow  for  their 
best  work,  especially  when  drawing 
from  long  suction-pipes ;  although  a  large  air-chamber  on  the  suction- 
pipe  near  the- pump  will  help  matters  in  regard  to  the  pounding  caused 


FIG.  101. — Basket-strainer. 


HO  THE  INJECTOR  AND  THE  STEAM-PUMP 

by  the  piston  by  rapid  motion  in  running  away  from  the  water- 
supply. 

In  the  pumping  of  hot  water  this  effect  is  so  strong  that  at  tem- 
peratures near  to  the  boiling-point  a  pump  will  not  lift  the  water; 
in  such  cases  the  pump  should  be  set  below  the  bottom  of  the  hot- 
water  tank. 

The  air-chamber  on  the  discharge  side  of  a  pump  performs  a 
most  important  service  in  equalizing  the  flow  of  water  through  long 
pipes  and  for  preventing  the  noise  and  hammering  in  the  pipe-lines 
by  the  elasticity  of  the  air  in  the  chamber  which  compensates  for  the 
intermittent  action  of  the  piston. 

The  volume  of  the  air-chamber  varies  in  different  makes  of  pumps 
from  2  to  3J  times  the  volume  of  the  water-cylinder  in  single-cylinder 
pumps,  and  from  1  to  2J  times  the  volume  of  the  water-cylinder  in 
the  duplex  type.  The  volume  of  the  water-cylinder  is  represented 
by  the  area  of  the  water-piston  multiplied  by  the  length  of  stroke. 

For  single-cylinder,  boiler-feed  pumps  and  those  employed  for 
elevator  and  similar  service  the  volume  of  the  air-chamber  should  be 
3  times  the  volume  of  the  water-cylinder,  and  for  duplex  pumps  not 
less  than  twice  the  volume  of  the  water-cylinder.  High-speed  pumps, 
such  as  fire-pumps,  should  be  provided  with  air-chambers  containing 
from  5  to  6  times  the  volume  of  the  water-cylinder. 

The  diameter  of  the  neck  should  not  exceed  one-third  the  diameter 
of  the  chamber.  When  the  pumps  work  under  pressure  exceeding 
85  or  90  pounds  per  square  inch,  it  is  frequently  found  that  the  air 
gradually  disappears  from  the  air-chamber,  the  air  passing  off  with 
the  water  by  absorption.  In  this  case  air  should  be  supplied  to  the 
air-chamber  unless  the  pump  runs  at  very  low  speeds,  say,  from  10  to 
20  strokes  for  the  smaller  sizes  and  from  3  to  5  strokes  per  minute 
for  pumping-engines.  At  higher  speed  and  with  no  air  in  the  air- 
chamber  the  valves  are  apt  to  seat  heavily  and  cause  more  or  less  jar 
and  noise,  and  the  flow  of  water  will  not  be  uniform.  In  large  pumping- 
plants  small  air-pumps  are  employed  for  keeping  the  air-chambers 
properly  charged.  In  smaller  plants  an  ordinary  bicycle-pump  and 
a  piece  of  rubber  tubing  are  used  to  good  advantage.  The  water- 
level  in  the  air-chamber  should  be  kept  down  to  from  one-fourth  to 
one-third  the  height  of  the  air-chamber  for  smooth  running  at  medium 
and  high  speeds. 


CHAPTER    VIII 

INCRUSTATION   IN   BOILERS,    AND    ITS   REMEDY 

APART  from  the  frequent  blowing  off  of  boilers  for  discharging  the 
floating  material  that  otherwise  would  settle  upon  the  tubes  or  plates 
and  form  incrusting  scale,  there  are  ingredients  needed  to  so  change 
the  chemical  combination  of  the  scale-forming  matter  that  it  may  be 
made  soluble  at  the  boiler  temperature  and  blown  out  or  changed  into 
solid  particles  that  do  not  crystallize  on  the  surface  of  tubes  and  plates, 
and  that  can  be  partially  blown  out  or  cleaned  out  at  stated  periods. 

A  knowledge  of  the  nature  of  the  scale-forming  material  in  water 
that  is  to  be  used  for  steam-making  is  essential,  and  if  this  cannot  be 
readily  obtained  from  tests,  a  sample  of  the  scale  may  give  a  clew  to 
its  chemical  composition.  The  principal  compounds  found  in  such 
material  are  carbonate  of  lime,  sulphate  of  lime,  carbonate  of  magnesia, 
and  sulphate  of  magnesia;  any  of  which  may  be  nearly  pure,  or  com- 
bined or  mixed  with  clay,  fine  sand,  or  mud,  which  tends  to  modify 
the  hardness  of  the  scale  or  settles  in  the  boiler  as  a  sludge.  The 
scale  from  water  containing  carbonate  of  lime  alone  is  not  as  hard  as 
the  scale  from  the  sulphate,  and  is  detached  much  easier.  The  sul- 
phate scale  may  be  recognized  by  its  sulphurous  fumes  when  heated. 

The  base  of  many  boiler-compounds  made  for  feeding  to  boilers 
with  the  water  is  carbonate  of  soda.  Caustic  soda  and  sodium 
tannate,  or  extract  of  oak,  sumac,  and  hemlock  bark — mixed  with  sal 
soda,  sal  ammoniac,  and  triphosphate  of  sodium — are  also  used.  For 
the  sulphate-of-lime  water  caustic  soda  gives  a  strong  reaction,  in 
which  sulphate  of  soda  is  formed — which  is  soluble — and  hydrate  of 
lime  falls  as  a  powder. 

PURIFICATION     OF     BOILER     FEED-WATER 

In  large  steam-plants  the  purification  of  the  water  before  feeding 
it  to  the  boilers  is  most  desirable  in  the  line  of  economy  and  dura- 
bility. For  this  purpose  a  water-purifying  apparatus  is  in  order,  and 

ill 


112 


INCRUSTATION   IN  BOILERS,   AND  ITS   REMEDY 


we  illustrate  in  Fig.  102  an  automatic  one  in  use  by  the  Chicago  & 
Northwestern  Railway  Co.  for  purging  the  water  for  their  locomo- 
tive service.  The  following  table  of  the  causes  of  incrustation  and 
corrosion,  with  their  effect  and  remedies  has  been  formulated  to  meet 
these  troubles  with  approved  treatment: 

TABLE  XVII. — CAUSES  OF  INCRUSTATION,  CORROSION,  AND  THEIR  REMEDIES. 


Cause  of  trouble. 

Incrustation. 

Treatment  of  water. 

Carbonate  of  lime  

Soft  scale  

Slaked  lime  sal-soda 

of  magnesia  

n          (i          n 

Sulphate  of  lime 

Hard  scale 

Sal-soda  caustic  soda 

'  '        of  magnesia 

« 

Slaked  lime  and  sal-soda 

Chloride  of  magnesia  

Corrosion  

Sal-soda,  or  caustic  soda. 

Sediment  Of  sand,  clay,  and  mud  •) 
Organic  matter                              •] 

Precipitation, 
or  soft  scale. 
Foaming    and 

j-  Alum,  and  filter. 
Slaked  lime,  sal-soda,  or  caustic 

Alkaline  water   

corrosion.  .  .  . 
Foaming          •< 

soda. 
Frequent  blowing  off  from  boiler, 
or  neutralize  with  hydrochloric 

Acid  waters   

Corrosion 

acid. 
Slaked  lime  sal-soda 

Triphosphate  of  sodium  may  be  also  used  instead  of  lime,  but  is 
somewhat  more  expensive  than  the  lime  treatment. 

In  the  use  of  a  purifying  apparatus  it  is  necessary  to  find  by  trial 
how  much  of  the  chemicals  is  required  in  a  saturated  mixture  with 
water,  which  should  be  stored  in  a  tank  from  which  the  proper 
quantity  may  be  automatically  drawn  and  mixed  with  the  water- 
supply  and  allowed  to  settle  in  large  tanks. 

In  Fig.  102  is  shown  a  cross-section  of  the  apparatus,  which  con- 
sists of  a  receiving-tank  for  the  chemicals,  a,  with  a  filter-screen  at  6, 
from  which  the  chemicals  are  drawn  into  a  stirring-tank  to  keep  the 
mixture  uniform,  whence  they  are  forced  to  flow  to  and  mix  with  the 
boiler-feed  water  at  a  uniform  rate  by  measurement  in  a  tilting- tank. 
By  opening  the  valve  e  this  solution  is  allowed  to  run  into  the  chemical 
tank  d.  To  thoroughly  mix  and  keep  the  solution  stirred  up  in  the 
chemical  tank  d,  stirring-blades  are  fixed  on  the  vertical  shaft  g, 
which  rotates  in  the  centre  of  this  tank.  In  order  to  measure  and 
deliver  predetermined  quantities  of  the  chemical  solution,  the  chem- 
ical tank  d  is  provided  with  two  pumps,  k  and  kl,  Fig.  103,  connected 
at  the  lower  portions  to  the  chemical  tank  d  through  .the  T's  I  and  I1. 


INCRUSTATION  IN  BOILERS,  AND  ITS  REMEDY 


113 


The  upper  portions  of  these  pumps  have  discharge-pipes,  m  and  m1, 
which  discharge  into  a  funnel,  n,  attached  to  an  elbow  terminating 
on  the  hard-water  supply-pipe,  so  that  just  before  the  hard  water 
passes  out  of  this  pipe  the  chemical  solution  is  mixed  with  it. 

To  obtain  the  best  results  it  is  essential  that  the  quantity  of  the 
standard  chemical  solution  and  hard  water  be  mixed  in  proper 
proportions,  and  also  that  this  be  done  regularly  whenever  the  ap- 
paratus is  being  used;  also  that  it  be  done  economically.  To  do 


FIG.  102. — Cross-sections  of  purifying  apparatus. 

this  a  tilting-vessel,  p,  Fig.  103,  is  used.  It  is  supported  on  a  shaft,  q, 
which  is  located  directly  under  the  elbow  from  which  the  mixed  hard 
water  and  chemical  solution  are  discharged. 

This  tilting-  and  measuring-vessel  is  divided  into  two  compart- 
ments of  equal  capacity,  p1  and  p2.  When  it  is  in  the  position  shown 
in  Fig.  103,  the  mixture  of  hard  water  and  chemicals  falls  from  the 
discharge-elbow  o  into  the  compartment  p1.  When  this  compart- 
ment is  nearly  filled  it  counterbalances  the  weight  of  the  other  com- 
partment, p2,  so  that  the  vessel  tilts  until  it  strikes  the  spring  30, 
emptying  the  contents  of  the  compartment  p1,  and  at  the  same  time 
bringing  the  other  compartment,  p2,  under  the  discharge-elbow  o. 
When  this  in  turn  is  filled  it  reverses  the  movement  of  the  tilting- 
vessel  p,  emptying  the  contents  of  the  compartment  p2,  and  bringing 
the  compartment  p1  again  under  the  elbow  o.  For  convenience  these 
compartments,  p1  and  p2,  are  made  of  such  size  that  100  gallons  of 


114 


INCRUSTATION  IN  BOILERS,   AND  ITS  REMEDY 


water  are  required  to  fill  them  to  the  point  where  they  commence  to 
tilt  and  empty  their  contents. 

Having  determined  the  amount  of  a  standard  solution  of  chemicals 
required  to  precipitate  the  scale-forming  compounds  from,  say,  100 
gallons  of  any  hard  water,  it  is  necessary  to  mix  it  with  the  100 
gallons  of  hard  water  in  one  of  the  compartments  pl  or  p2.  This  is 


FIG.  103. — Elevation-tanks  and  pump. 

done  by  regulating  the  length  of  the  stroke  of  the  pumps  k  and  klT 
which  pump  the  standard  chemical  solution  from  the  tank  d  into  the 
funnel  n.  These  pumps,  k  and  kl,  are  operated  by  the  tilting-vessel 
p  in  the  following  manner: 

The  plungers  u  are  connected  to  a  walking-beam,  v,  which  is  rotably 
mounted  on  the  shaft  w.  The  ends  of  this  walking-beam  are  con- 
nected, by  means  of  the  chains  x  and  x1,  with  studs,  x2,  on  each  end  of 
the  tilting-vessel.  If  the  parts  are  in  the  position  shown  in  Fig.  103, 
when  the  tilting-vessel  p  is  tilted  downwardly  to  the  left  the  plunger 
of  the  pump  k  is  raised  so  that  a  quantity  of  the  standard  chemical 
solution  is  delivered  into  the  funnel  n,  and  flows  with  the  hard  water 
into  the  compartment  p2.  When  100  gallons  are  in  it,  the  tilting- 
vessel  p  operates  in  the  opposite  direction,  causing  the  other  pump,. 
k1,  to  operate,  and  delivers  a  quantity  of  the  standard  chemical  solu- 
tion into  the  funnel  n,  whence  it  flows  with  the  hard  water  into 
the  compartment  p1.  It  will  be  understood  that  the  hard  water  is 
running  constantly  through  the  elbow  o,  and  that  the  two  pumps  k 
and  A;1  are  intermittent  in  their  action.  The  quantity  of  the  standard 


INCRUSTATION  IN  BOILERS,  AND  ITS  REMEDY  115 

chemical  solution  delivered  at  each  stroke  of  these  pumps  is  regulated 
by  the  length  of  the  strokes.  This  can  be  adjusted  by  the  length  of 
the  chains  x  and  xl,  so  that  a  predetermined  quantity  of  chemical 
solution  will  be  delivered  at  each  stroke.  From  this  description  it 
will  readily  be  seen  that  a  fixed  quantity  of  chemical  solution  is  dis- 
charged into  the  elbow  o  and  flows  with  the  hard  water  into  each 
compartment  of  the  tilting-vessel  p,  in  proportion  to  the  amount  of 
hard  water  that  is  required  to  cause  this  vessel  to  tilt? 

It  is  desirable  to  automatically  and  economically  operate  the 
vertical  shaft  g  in  the  chemical  tank  d,  so  that  the  horizontal  blades 
attached  to  it  will  keep  the  chemical  mixture  thoroughly  agitated. 
To  do  this  it  is  geared  to  the  horizontal  shaft  w  by  the  pinions  y  and  yl. 
The  other  end  of  the  horizontal  shaft  w  is  provided  with  a  sprocket- 
wheel,  y2,  around  which  a  link-belt  chain  passes,  the  ends  of  this  chain 
being  attached  to  the  ends  of  the  tilting-vessel  by  the  studs  y4.  It 


FIG.  104. — Pump-house  and  settling-tanks. 

will  readily  be  seen  by  this  arrangement  that  whenever  the  tilting- 
vessel  p  moves,  the  stirring-blades  attached  to  the  vertical  shaft  g 
in  the  chemical  tanks  also  move,  thus  agitating  the  chemical  mixture 
in  the  tank  d. 

For  convenience  in  measuring  the  height  in  the  tank  of  this 
chemical  mixture,  a  pipe,  z,  Fig.  103,  is  attached  to  the  side  of  the  tank 
d  near  its  bottom.  In  this  pipe  is  a  float,  z1,  attached  to  a  graduated 
scale,  z2,  from  which  can  be  read  the  quantity  of  liquid  in  the  tank  d. 


116  INCRUSTATION  IN  BOILERS,   AND   ITS   REMEDY 

The  above-described  apparatus  automatically  mixes  the  proper 
quantity  of  the  chemical  solution  with  each  100  gallons  of  hard 
water  delivered  by  the  steam-pump,  and  utilizes  the  weight  of  the 
water  to  furnish  power  to  operate  it.  The  result  of  this  mixture  is 
that  the  scale-forming  matter  that  was  in  solution  in  the  hard  water 
is  thrown  out  of  solution,  but  remains  in  suspension  in  the  treated 
water.  This  is  separated  from  the  treated  water  in  the  following 
manner : 

By  referring  to  Fig.  104  it  will  be  seen  that  the  apparatus  is  located 
in  the  second  story  of  the  pump-house,  and  that  the  pump-house  is 
located  between  two  tanks  placed  on  the  ground.  The  tilting-vessel 
above  described  empties  its  contents  into  a  wooden  box  which  is 
provided  with  troughs  leading  to  the  two  settling-tanks.  These 
troughs  are  provided  with  shut-off  gates,  so  that  the  water  can  be  run 
into  whichever  tank  is  desired.  It  will  be  seen  that  the  troughs 
empty  their  contents  into  vertical  pipes  that  extend  to  the  bottom 
of  the  tanks  and  terminate  in  elbows,  so  as  not  to  disturb  the  clear 
water  drawn  from  the  top. 

The  water  for  boiler  use  is  drawn  from  the  float-nozles  at  the 
surface  of  the  water,  which  swing  downward  as  the  water-level  is 
drawn  down.  The  tanks  are  cleaned  alternately. 

From  records  of  many  trials  of  the  effect  of  incrustation  on  fuel- 
consumption  in  Europe  and  the  United  States,  it  has  been  found  that 
there  is  an  average  loss  of  15  per  cent,  in  full  by  y^-inch  scale,  and 
a  greater  loss  as  the  scale  thickens. 

THE     FACTOR     OF     EVAPORATION 

To  determine  the  efficiency  of  a  boiler,  or  the  amount  of  water 
evaporated  by  a  pound  of  fuel,  it  is  necessary  to  reduce  the  amount 
of  evaporation  which  actually  takes  place  from  the  temperature  of 
the  feed-water  at  the  temperature  of  the  steam,  to  an  equivalent 
amount  at  and  from  212°  F.  The  factor  of  evaporation  at  212°  F. 
and  atmospheric  pressure  =1.00. 

Then  from  the  total  heat-units  in  Column  6  of  Table  XX  of  the 
properties  of  saturated  steam  for  any  absolute  pressure,  subtract 
the  heat-units  in  the  feed-water  from  32°  F.  to  its  temperature;  divide 
the  remainder  by  the  constant  966.1  (the  latent  heat  of  steam  at  212° 


INCRUSTATION  IN  BOILERS,   AND  ITS   REMEDY  117 


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118  INCRUSTATION  IN  BOILERS,   AND  ITS   REMEDY 

F.),  and  the  quotient  will  give  the  factor  of  evaporation  as  per  Table 
XVIII.  For  example:  the  factor  of  evaporation  for  100  pounds  abso- 
lute pressure — 85.3  gauge-pressure — from  water  at  212°  F.  and  feed- 
water  at  100°  F.,  will  be  ^^^=1.153,  as  in  the  table,  Column 

9bo.l 

100,  and  opposite  100°  F.  in  the  first  column. 

The  total  heat-units  from  the  feed-water  temperature  in  the 
steam,  at  any  given  pressure,  may  be  readily  obtained  by  multiplying 
the  total  heat-units  at  212°  F.  as  a  constant  (966.1),  by  the  factor  of 
evaporation  for  the  feed-water  temperature  in  the  first  column  at 
the  intersection  of  its  line  in  the  columns  of  absolute  pressure,  Table 
XVIII. 

Intermediate  temperatures  and  pressures  may  be  obtained  by 
interpolation.  The  use  of  the  factor  of  evaporation  is  apparent  as  a 
ready  method  for  obtaining  the  actual  number  of  pounds  of  water 
evaporated  in  a  boiler  from  and  at  a  temperature  of  212°  F.  per 
pound  of  coal  or  of  combustible,  if  the  combustible  value  of  the  coal 
is  known. 

For  example:  with  feed-water  at  100°  F.,  average  steam-pressure 
during  trial  75.3  gauge  =  90  pounds  absolute,  with  say  40  pounds  coal 
burned  for  any  unit  of  time  and  340  pounds  of  water  fed  to  the  boiler  for 
the  same  unit  of  time;  then  ^-  =  8.5  pounds  of  water  evaporated  at 
100°  F.  per  pound  of  coal.  Then  for  the  evaporation  from  and  at 
212°  F.,  the  factor  of  evaporation  for  100°  and  90  pounds  is  by  the 
table  1.151,  and  8.5x1.151  =  9.27  pounds  water  evaporated  at 
212°  F. 

THE     JET-CONDENSER 

Where  a  sufficient  quantity  of  water  suitable  for  boiler-feeding 
purposes  is  available,  the  jet-condenser,  being  the  simplest  and  easiest 
to  operate,  is  preferable.  Where,  however,  water  suitable  for  boiler- 
feeding  is  not  available,  a  surface-condenser  may  be  used.  In  this 
type  the  steam  is  condensed  in  a  condensing-chamber  on  the  surface 
of  tubes  through  which  cold  water  is  circulating,  and  the  distilled 
water  so  furnished  may  be  again  fed  to  the  boilers.  Where  any  con- 
siderable amount  of  cylinder-oil  is  used,  some  provision  must  be 
made  with  surface-condensers  to  remove  this  oil  before  the  water  is 
fed  to  the  boilers.  With  either  type  the  quantity  of  water  to  be 


INCRUSTATION  IN  BOILERS,  AND   ITS   REMEDY 


119 


circulated  through  the  condenser  should  be  from  twenty  to  forty 
times  the  quantity  of  steam  to  be  condensed,  depending  upon  the 
temperature  of  the  water  available  for  condensing  purposes. 

Condenser  manufacturers  have  recently  introduced  several  types 
of  self-cooling  condensers  by  which  the  hot  water  delivered  from  the 
condenser-pumps  can  be  cooled  and  reused,  so  that  with  water  suffi- 
cient in  quantity  for  boiler-feed  purposes  only,  the  plant  may  be 
located  at  any  convenient  point  and  still  retain  the  fuel-saving  and 
.other  benefits  of  high  steam-pressures  and  con- 
densers. 

The  condenser-head,  shown  in  section  in  Fig. 
105,  consists  of  a  suitable  steam-chamber,  usually 
in  the  form  of  a  large  return-bend.  This  is  fitted 
with  a  relief -valve  at  the  top  which  closes  auto- 
matically, due  to  its  own  weight  aided  by  a  light 
spring.  When  a  vacuum  exists  in  the  condenser- 
head,  the  valve  is  pressed  more  firmly  against  its 
seat  by  atmospheric  pressure  of  about  15  pounds 
per  square  inch. 

Connected  with  one  of  the  openings  in  the 
steam-chamber,  or  return-bend,  is  the  regulating- 
nozle,  which  is  movable  vertically  and  is  raised  by 
means  of  a  threaded  stem  and  hand-wheel.  The 
nozle  regulates  the  width  of  the  inlet-orifice  for  the  condensing  water 
according  to  the  load,  the  water  entering  the  side  of  the  nozle-chamber 
and  surrounding  the  nozle,  flows  in  a  thin  sheet  or  film  through  the 
annular  orifice  formed  between  the  nozle  and  its  seat. 

Below  the  chamber  is  connected  the  throat  or  combining-tube, 
the  bore  of  which  gradually  contracts  toward  the  middle  of  its  length 
and  then  enlarges  toward  the  lower  end,  where  it  is  connected  to 
the  tail-pipe,  which  extends  to  34  feet  below  the  nozle  and  dips  into 
the  hot-well  for  the  purpose  of  a  water-seal  to  prevent  air  entering 
the  pipe  and  to  resist  the  atmospheric  pressure  from  without.  There- 
fore, if  the  tail-pipe  were  less  than  34  feet  long,  measured  between 
the  points  mentioned,  water  supplied  to  the  condenser  would  not 
leave  the  latter  without  the  use  of  a  pump.  But  with  a  fall  of  34 
feet,  a  given  quantity  of  water  admitted  around  the  hollow  cone,  or 
nozle,  causes  the  discharge  of  a  corresponding  amount  into  the  hot- 


FIG.  105. — Siphon 
condenser. 


120 


INCRUSTATION  IN  BOILERS,  AND  ITS  REMEDY 


well,  so  that  the  level  in  the  condenser  never  can  rise  to  the  water- 
inlet. 

Water  passing  through  the  annular  orifice  formed  by  the  hollow 
cone  flows  downward  in  a  cone-shaped  film  into  the  contracted  throat, 
where  its  velocity  is  sufficiently  increased  to  enable  it  to  carry  air 
along  with  it,  thus  producing  a  vacuum  in  the  exhaust-pipe.  Steam 


Overflo 


Hot  Well 

FIG.  106. — Siphon  condenser  connected. 

flows  downward  through  the  regulating-nozle  and  into  the  cone-shape 
film  of  water,  where  it  is  condensed.  The  continuous  condensation 
of  steam  and  the  ability  to  get  rid  of  the  water  may  sometimes  cease, 
when  the  exhaust-valve  will  be  raised,  allowing  the  steam  to  escape 
into  the  atmosphere.  If  it  becomes  necessary  to  break  the  vacuum, 
the  relief-valve  can  be  opened  from  the  engine-room  floor  by  means 
of  chains  connected  with  a  lever  attached  to  the  valve.  There  are  a 


INCRUSTATION  IN  BOILERS,  AND   ITS  REMEDY          121 

number  of  this  type  of  condensers,  of  various  models,  on  the  market, 
all  involving  the  same  principles  as  here  shown. 

The  ejector-condenser,  Fig.  107,  is  of  the  Korting  type,  with  a 
three-way  valve  by  which  the  exhaust-steam  is  passed  to  the  atmos- 
phere or  is  condensed  by  the  multiple-nozle  water-jet.  The  high 
velocity  of  the  water- jet  past  the  angular  orifices  in  the  nozle  main- 
tains the  required  vacuum  without  recourse  to  a  pump  or  long  vertical 
pipe. 

A  sectional  view  of  a  Worthington  direct-acting  jet-condenser  is 
given  in  Fig.  108.  In  all  essential  features  it  is  a  duplex,  direct-acting 


FIG.  107. — Ejector-condenser. 


FIG.  108. — Jet-condenser  pump. 


pump  with  a  condensing-chamber  or  cone  connected  with  the  pump- 
suction  or  suction-chamber.  The  exhaust-pipe  from  the  engine  is 
connected  at  A,  and  the  pipe  supplying  the  injection- water  is  con- 
nected at  B,  which  point  on  the  condenser  should  never  be  more  than 
18  feet  above  the  surface  of  the  water  from  which  the  supply  of  con- 
densing water  is  to  be  drawn.  The  discharge  from  the  condenser 
flows  out  at  J  through  a  pipe  leading  to  the  hot-well. 

When  the  pump  is  started,  a  partial  vacuum  is  created  in  the 
suction-chamber  above  the  valves  H,  H,  in  the  cone  F,  in  the  exhaust- 
pipe  at  A,  and  in  the  injection-pipe  connected  at  B.  As  soon  as  suffi- 
cient air  has  been  exhausted,  water  begins  to  flow  through  the  pipe  C 


122  INCRUSTATION  IN  BOILERS,  AND  ITS  REMEDY 

and  the  spray-nozle  D.  Continued  motion  of  the  pump  increases 
the  vacuum  up  to  the  working  point,  26  or  27  inches.  Water  issuing 
from  the  nozle  D  is  broken  into  a  fine  spray  which  completely  fills 
the  condensing-chamber  or  cone  beneath  it,  so  that  upon  starting 
the  engine  the  exhaust-steam  is  compelled  to  flow  into  the  spray  of 
cold  water. 

The  mixture  of  condensed  steam  and  injection  flows  downward 
through  the  tapered  throat  F  into  the  suction-chamber  of  the  pump 
with  sufficient  velocity  to  carry  with  it  any  air  that  may  have  leaked 
into  the  exhaust-pipe,  together  with  the  air  brought  in  with  the  injec- 
tion-water. The  direction  of  the  water  in  the  pump  may  be  easily 
traced,  the  pump  discharging  both  water  and  air  through  the  dis- 
charge-valves I,  I  and  outlet  J. 

Many  manufacturers  of  pumps  are  now  making  the  condenser 
attachments  to  their  vacuum-pumps. 


WATER   REQUIRED   FOR   CONDENSING  THE 
EXHAUST 

Evidently  the  heat  given  up  by  the  steam  must  equal  the  heat 
gained  by  the  cooling  water,  and  for  each  pound  of  steam  condensed 
there  will  be  a  certain  number  of  pounds  of  cooling  water  used  under 
a  given  set  of  conditions.  This  makes  it  possible  to  determine  the 
theoretical  ratio  between  the  weight  of  condensed  steam  and  the 
weight  of  cooling  water  used,  and  this  theoretical  ratio  will  for  the 
jet-condenser  correspond  to  the  actual  ratio.  For  the  surface-con- 
denser the  amount  of  cooling  water  used  will  be  about  20  per  cent, 
in  excess  of  the  theoretical  value. 

The  heat  removed  from  a  pound  of  steam,  with  variable  terminal 
pressure,  is  but  slight  within  practical  limits.  For  instance,  at  30 
pounds  absolute  terminal  pressure,  the  heat  contained  is  1,190.3 
thermal  units,  while  at  5  pounds  absolute  pressure  it  is  1,163.5  thermal 
units,  a  difference  of  a  little  over  2  per  cent. ;  hence,  it  is  not  necessary 
to  figure  on  small  differences  in  terminal  pressure.  Table  XIX  shows 
the  ratio  of  the  cooling  water  to  the  condensed  steam,  or,  in  other 
words,  the  number  of  pounds  of  cooling  water  needed  per  pound  of 
steam  for  the  terminal  pressure  of  15  pounds  absolute,  and  for  final 
temperatures  of  the  condensed  steam  from  90°  to  134°  F. 


INCRUSTATION  IN  BOILERS,  AND   ITS  REMEDY 


123 


TABLE  XIX. — POUNDS  OF  WATER  REQUIRED  TO  CONDENSE  1  POUND   OF  STEAM 
AT  EXHAUST-PRESSURE  OF  15  POUNDS  ABSOLUTE,  IN  JET-CONDENSERS. 


la, 

ENTERING  TEMPERATURE  OF  INJECTION-WATER. 

||« 

35 

40 

45 

50 

55 

60 

65 

70 

75 

80 

85 

90 

f.Ej 

JH 

Pounds  of  condensing  water  required  per  pound  of  steam. 

90 

20.0 

22.0 

24.4 

27.5 

31.4 

36.7 

44.0 

55.0 

73.3 

110.0 

220.0 

92 

19.2 

21.1 

23.4 

26.1 

29.7 

34.3 

40.7 

49.9 

64.6 

91.5 

156.8 

549.0 

94 

18.6 

20.3 

22.4 

24.9 

28.1 

32.2 

37.8 

45.7 

57.7 

78.1 

121.8 

274.0 

96 

17.9 

19.5 

21.4 

23.6 

26.7 

30.4 

35.3 

42.1 

52.1 

68.4 

99.4 

182.3 

98 

17.3 

18.8 

20.6 

22.7 

25.4 

28.7 

33.1 

39.0 

47.5 

60.7 

84.0 

136.5 

100 

16.8 

18.2 

19.8 

21.1 

24.2 

27.2 

31.1 

36.3 

43.6 

54.5 

72.7 

109.0 

102 

16.2 

17.5 

19.1 

20.9 

23.1 

25.9 

29.4 

34.0 

40.3 

49.5 

64.0 

90.7 

104 

15.7 

17.0 

18.4 

20.1 

22.2 

24.7 

27.8 

31.9 

37.4 

45.2 

57.2 

77.6 

106 

15.3 

16.4 

17.8 

19.4 

21.3 

23.6 

26.4 

30.1 

35.0 

41.7 

51.6 

67.7 

108 

14.8 

15.9 

17.2 

18.7 

20.4 

22.5 

25.2 

28.5 

32.8 

38.6 

47.0 

60.1 

110 

14.4 

15.4 

16.6 

18.0 

19.6 

21.6 

24.0 

27.0 

30.9 

36.0 

43.2 

54.0 

112 

14.0 

15.0 

16.1 

17.4 

18.9 

20.7 

22.9 

25.7 

29.1 

33.6 

39.9 

49.0 

114 

13.6 

14.5 

15.6 

16.8 

18.2 

19.9 

22.0 

24.5 

27.6 

31.6 

37.1 

44.8 

116 

13.3 

14.1 

15.1 

16.3 

17.6 

19.2 

21.1 

23.3 

26.2 

29.8 

34.6 

41.3 

118 

12.9 

13.7 

14.7 

15.8 

17.0 

18.5 

20.2 

22.3 

24.9 

28.2 

32.5 

38.3 

120 

12.6 

13.4 

14.3 

15.3 

16.5 

17.8 

19.5 

21.4 

23.8 

26.7 

30.6 

35.7 

122 

12.3 

13.0 

13.9 

14.8 

15.9 

17.2 

18.7 

20.5 

22.7 

25.4 

28.9 

33.4 

124 

12.0 

12.7 

13.5 

14.4 

15.4 

16.7 

18.1 

19.7 

21.8 

24.2 

27.3 

31.4 

126 

11.7 

12.4 

13.1 

14.0 

15.0 

16.1 

17.4 

19.0 

20.9 

23.1 

26.0 

29.6 

128 

11.4 

12.1 

12.8 

13.6 

14.5 

15.6 

16.9 

18.3 

20.0 

22.1 

24.7 

27.9 

130 

11.2 

11.8 

12.5 

13.2 

14.1 

15.1 

16.3 

17.7 

19.3 

21.2 

23.6 

26.5 

132 

10.9 

11.5 

12.2 

12.9 

13.7 

14.7 

15.7 

17.1 

18.6 

20.3 

22.5 

25.2 

134 

10.7 

11.2 

11.9 

12.6 

13.4 

14.3 

15.3 

16.5 

17.9 

19.6 

21.6 

24.0 

This  table  has  been  computed  from  the  formula  Q  = 


190  _ 
L=— 
1  —  t 


n 


which  Q  =  quantity  of  water  in  pounds  to  condense  1  pound  of  steam, 
or  25.85  cubic  feet  at  exhaust  temperature  of  213.1°  F.;  T  =  tempera- 
ture of  water  discharged  from  the  condenser;  t  =  the  difference  in 
temperature  between  the  injection-  and  the  discharge-water,  and 
1,190  =  the  total  heat  of  the  steam,  plus  the  loss  from  radiation  in  the 
operation  of  the  condenser. 

The  surface-condenser,  so  useful  in  the  line  of*  economy  where 
the  cost  of  water  claims  a  saving  of  its  waste  in  the  jet-condenser, 
comes  to  the  front  in  connection  with  the  cooling-tower  as  an  econo- 
mizer in  the  generation  of  steam-power.  There  are  a  number  of 
models  in  design  with  claims  of  efficiency. 

In  Fig.  109  is  shown  a  two-section  condenser  with  a  cast-iron  shell 
and  brass  tubes.  The  difference  in  expansion  between  the  brass 


124 


INCRUSTATION  IN  BOILERS,  AND   ITS   REMEDY 


tubes  and  the  cast-iron  shell  is  provided  for  by  stuffing-boxes  and 
glands  at  one  or  both  ends.     The  cooling  water  enters  through  the 


FIG.  109. — Surface-condenser. 

lower  tier  and  discharges  through  the  upper  one  for  the  best  efficiency 
of  the  condenser,  with  the  steam  passing  in  the  opposite  direction. 

A  three-section  surface-condenser  and  heater  is  shown  in  Fig. 
110.  The  upper  section  is  divided  in  two  parts  as  a  feed-water  heater, 
through  which  part  of  the  water  used  for  condensing  is  passed  through 


FIG.  110. — Combination  condenser. 

one  part  of  the  upper  section  and  returned  by  the  other  side-chamber. 
By  this  arrangement  the  feed-water  is  heated  to  as  high  a  tempera- 
ture as  practicable  by  first  contact  with  the  exhaust-steam. 

The  double- tube  type,  Fig.  Ill,  is  one  in  which  the  shell  encloses 
both  tube-heads  at  one  end,  in  one  of  which  the  central  tubes  are 
carried  through  the  inner  compartment,  and  both  inner  and  outer 
concentric  tubes  are  expanded  in  their  respective  heads. 

The  outside  tubes  are  capped  or  welded  close  at  their  farther 
ends.  The  circulation  is  made  complete  by  its  discharge  from  the  inner 


INCRUSTATION  IN   BOILERS,  AND  ITS  REMEDY 


125 


to  the  outer  tube,  which  is  the  condensing-surface;  thus  all  troubles 
from  expansion  are  avoided. 

A  novel  system  of  surface-condensation  is  shown  in  Fig.  112,  in 
which  a  cylinder  is  filled  with  small  brass  tubes,  open  for  receiving  a 
spray-jet  of  water  at  one 
end;  a  cone  and  suction- 
blower  are  at  the  other 
end,  as  well  as  the  usual 
vacuum-pump.  In  its  ac- 
tion a  spray-jet  of  water  is 
thrown  against  the  tubes  at 
one  end,  and  with  a  large 
volume  of  air  is  drawn 
through  the  tubes  by  a 
suction-blower  at  the  end 
of  the  conical  chamber. 

The  water  is  vaporized,  and  with  the  air  takes  up  the  heat  of  the 
exhaust-steam,  which  is  discharged  in  a  vapor  by  the  blower.  The 
economical  claim  for  this  arrangement  is  that  but  1  pound  of  water  is 
used  for  condensing  1  pound  of  steam. 


FIG.  111. — Concentric  tube-condenser. 


FIG.  112. — Spray  surface-condenser. 

The  large  number  of  oil-extracting  devices  on  the  market,  of  various 
models,  need  no  discussion  as  to  their  merits,  as  each  has  a  claim  to 
be  the  best.  They  are  a  great  need  and  in  general  use,  and  are  usually 
connected  in  the  exhaust-pipe  near  the  surface-condenser.  The  leading 
principle  of  action  of  these  separators  is  their  sudden  deflection  of 
the  passing  steam  by  an  apron,  which  may  be  curved  or  flat,  pierced 
with  slots,  holes,  or  with  corrugated  surfaces,  arranged  to  catch  the 
oil  and  drain  it  to  a  receptacle  below. 


126 


INCRUSTATION   IN  BOILERS,  AND   ITS  REMEDY 


In  Fig.  113  is  shown  a  vertical  and  a  horizontal  pattern  of  the 
Austin  Separator  Co.,  and  in  Fig.  114  a  separator  of  the  Lippincott 
pattern,  with  a  broad  spherical  apron  at  A  and  catch-plates  at  B,  C,  D, 
the  steam  being  deflected  around  the  outside  of  the  spherical  plate  A. 


FIG.  113. — Oil-separators. 


FIG.  114. — Lippincott  separator. 


A  combined  vacuum  air-pump  and  water-circulating  pump  for 
large  condensing-engines  is  shown  in  Fig.  115.  It  is  of  the  Conover 
type  of  the  Watson  Machine  Co.  Its  compact  design  makes  it  a  good 
study  for  the  student  and  engineer.  It  is  operated  by  a  pair  of 

compound  Corliss  cylinders,  with 
dash-pots  complete.  The  beam- 
ends  connect  with  the  steam- 
cylinders,  and  at  mid-distance 
to  its  centre  are  connected  to  the 
pumps,  and  from  one  of  these  to 
the  crank,  the  shaft  of  which  is 
seen  in  the  centre  of  the  illustra- 
tion. The  shaft  carries  a  fly- 
wheel at  the  rear  end  and  drives 
the  governor.  The  air-pump  is 
single-acting;  the  circulating- 
pump  is  a  double-acting  trunk 
pattern,  located  at  the  right. 
The  receiver  is  attached  to  the 
frame  just  below  the  beam.  This  type  of  air-  and  circulating-pumps 
is  made  for  engines  of  from  5,000  to  20,000  horse-power. 


Air  Bump  Circulating  Pump 

Fro.  115. — Air-  and  circulating-pump. 


INCRUSTATION   IN  BOILERS,  AND  ITS   REMEDY 


127 


FIG.  116.— Edwards's 
air-pump. 


A  novel  air-pump  for  medium-sized  condensing-engines  is  the 
Edwards  type,  Fig.  116,  which  has  no  suction-valves.  Ports  around 
the  cylinder  are  opened  by  passing  the  piston  past  them  to  the  bottom 
of  the  cylinder. 

The  water  and  air  enter  above  the  piston  and  are  discharged 
through  valves  above,  which  are  water-sealed;  the  discharged  water 
flowing  over  a  dam,  as  shown  by  the  arrow.  A 
water-filled  cup  seals  the  piston-rod  below  the 
stuffing-box  gland.  The  descent  of  the  piston 
forms  a  vacuum  above  it,  which  is  a  powerful 
draught  at  the  moment  of  opening  of  the  cylin- 
der-ports by  the  piston. 

WATER-COOLING     TOWERS 

The  saving  of  water  in  locations  where  it  is 
deficient  for  the  necessities  of  steam-power  is  a 
matter  of  great  importance,  as  in  arid  regions,  and 
of  economy,  where  its  cost  is  of  material  amount. 

The  main  feature  of  the  cooling-tower  is  derived 
from  the  intimate  contact  of  cool  air,  circulated  by 
a  fan  driven  by  any  convenient  power,  or  by  the 
natural  draught  caused  by  the  heating  of  the  air 
by  contact  of  the  falling  spray  or  sheets  of  hot 
water.  In  this  manner  the  hot  water  from  a  jet-  or 
surface-condenser  may  be  cooled  sufficiently  for 
use  again  in  the  condenser. 

The  cooling- towers  are  filled  in  a  variety  of 
material  and  forms,  such  as  hanging  curtains  of 
galvanized-iron  netting,  or  strips  of  thin  wood  and 
tile  in  tiers  crossing  each  other,  so  arranged  as  to 
give  the  greatest  wet  surface  and  also  the  greatest 
area  of  airway. 

In  Fig.  117  we  illustrate  by  a  section  the 
Worthington  water-cooling  tower,  which  consists 
of  a  cylindrical  steel  shell  open  at  the  top,  sup- 
ported upon  a  suitable  foundation,  and  having  fitted  at  one  side 
a  fan,  the  function  of  which  is  to  circulate  a  current  of  air  through 


FIG.  117. — Air-cool- 
ing tower. 


128 


INCRUSTATION  IN  BOILERS,   AND  ITS  REMEDY 


the  tower  and  filling  This  filling  consists  of  layers  of  cylindrical 
tubular  tiling,  which  rest  upon  a  grating  supported  by  a  brick  wall 
extending  around  the  circumference  of  the  tower.  The  heated  dis- 
charge-water from  the  condenser  enters  the  tower  at  the  side,  passes 
up  the  central  pipe,  and  is  delivered  on  the  upper  layer  of  tiling  and 
over  the  whole  cross-section  of  the  tower  by  a  distributing  device  con- 


Natural  Draft 
Cooling  Tower 


Cold  Well 


Overflow 


Hot  Well 

FIG.  118. — High-vacuum  installation  with  cooling-tower. 

sisting  of  four  pipes,  which  are  caused  to  rotate  about  the  central 
water-pipe  by  the  simple  reaction  of  the  jets  of  heated  water  issuing 
from  one  side  of  each  pipe.  The  water  thus  delivered  spreads  over 
the  outside  and  inside  surfaces  of  the  walls  of  the  tiling  and  forms  a 
continuous  sheet,  which  is  presented  to  the  action  of  the  air. 

In  Fig.  118  is  represented  a  complete  power-plant  of  the  Worth- 
ington  model  with  a  jet  or  barometric  condenser,  natural  draught- 
cooling  tower,  combined  hot-  and  cold-water  pump,  and  a  vacuum- 
pump. 


INCRUSTATION  IN  BOILERS,   AND  ITS  REMEDY  129 

It  will  be  seen  on  inspection  that  the  exhaust  from  one  or  a  series 
of,  engines  passes  into  a  trunk-pipe  from  which  a  rising  pipe  leads  to 
the  head  of  the  ejector-condenser  and  on  to  a  relief-valve.  The  cold- 
water  cylinder  of  the  circulating-pump  takes  its  suction  from  the  cold- 
water  well  in  the  tower  and  discharges  into  the  head  of  the  jet-con- 
denser. The  hot-water  cylinder  of  the  same  pump  takes  its  suction 
from  the  hot-well  of  the  condenser  and  discharges  at  the  top  of  the 
tower  in  fine  streams  that  trickle  over  the  surface  of  the  tiling  in 
contact  with  the  up-flowing  air.  In  order,  however,  to  obtain  the 
highest  vacuum  without  using  an  abnormal  amount  of  water  to  carry 
off  the  air,  a  separate  dry-vacuum  pump  is  used,  as  shown  in  the 
illustration.  The  air  that  is  not  carried  off  by  the  water  is  taken 
from  the  space  under  the  spray-cone  in  the  condenser.  By  this  means 
it  is  possible  to  get  as  much  as  29  inches  of  vacuum  under  the  most 
favorable  conditions. 

The  loss  of  water  is  minimized  in  this  arrangement  to  the  amount 
vaporized  to  the  air  in  the  cooling-tower  and  the  leakages. 


CHAPTER    IX 

STEAM   ABOVE   ATMOSPHERIC   PRESSURE 

STEAM  under  pressure  and  confined,  as  in  a  boiler,  has  a  potential 
energy  due  to  its  pressure,  which  becomes  kinetic,  a  moving  force, 
when  following  the  piston  of  an  engine  from  the  boiler-pressure  or  by 
its  force  of  expansion. 

Steam,  like  fluids  under  pressure,  becomes  a  force  by  momentum 
from  its  pressure  and  expansive  velocity  when  impinging  on  the 
blades  of  the  steam-turbine. 

The  derivation  of  its  energy,  both  potential  and  kinetic,  is  from 
heat  in  its  specific  and  latent  forms,  which,  combined  with  water, 
gives  it  the  elastic  properties  produced  in  its  vapor. 

Heat  is  the  basis  of  energy  in  nature,  in  life,  and  in  work  of  the 
most  important  value  to  our  industries;  it  has  a  measured  value, 
the  heat-unit  or  British  thermal  unit,  equivalent  to  the  amount 
received  to  raise  1  pound  of  water  at  the  temperature  of  its  greatest 
density,  39°  F.,  through  1  degree  of  the  Fahrenheit  scale. 

DIAGRAM     OF     STEAM -GENERATION 

The  rise  in  temperature  of  water  in  its  frozen  state  from  absolute 
zero,  its  absorption  of  heat  in  thermal  units,  its  further  absorption  of 
heat  in  melting  and  rise  of  temperature  to  its  boiling-point,  and  its 
conversion  into  steam,  are  graphically  shown  in  the  diagram  (Fig.  119) 
in  which  the  vertical  scale  represents  the  temperature  from  absolute 
zero,  and  the  horizontal  scale  the  heat-units  absorbed  during  the 
change  from  ice  to  steam. 

The  divergent  lines  at  the  right  show  the  thermal-heat  difference 
of  steam  at  constant  volume  (Cv)  and  constant  pressure  (Cp).    All  the 
inclined  lines  should  be  slightly  curved  to  show  the  change  in  specific 
heat,  but  it  is  not  readily  shown  on  so  small  a  diagram. 
130 


STEAM  ABOVE  ATMOSPHERIC  PRESSURE 


131 


Steam  is  treated  in  its  work  under  different  conditions,  essential 
to  its  economical  use: 

1.  As  saturated  steam;  its  condition  when  generated  in  quiet 
contact  with  its  water  of  generation. 

2.  As  wet  steam;  its  condition  when  by  the  violent  action  of 
its  generation  from  an  overworked  or  foaming  boiler  it  is  loaded 
with    minute    vesicles    of 

water  containing  no  latent 
heat  and  consequently  non- 
expansive  in  its  working 
economy;  although  its  spe- 
cific heat  at  high  press- 
ures and  temperatures 
may  evolve  a  minute  por- 
tion of  the  water-vesicle 
into  vapor  during  expan- 
sive work. 

3.  As  dry  steam;  its  con- 
dition when  it  contains  no 
vesicular  moisture;  it  may 
be  saturated  steam  or  with 
initial  or  expansive  super- 
heat. 

4.  As   superheated 
steam,  which  is  at  a  tem- 
perature above  that  of  the 
water    from    which    it    is 
generated,  either  by  some 
peculiar    boiler    construc- 
tion, or   at   a  temperature  largely  increased  by  passing  through  a 
superheater. 

The  temperature  of  water  and  its  steam  when  confined  in  contact 
and  under  pressure  may  be  computed  from  the  sixth  root  of  the 
absolute  pressure  in  inches  of  mercury,  or  the  absolute  pressure  in 
pounds  per  square  inch  multiplied  by  2.036.  Multiply  the  sixth  root 
of  this  product  by  176.4,  and  from  the  last  product  subtract  100  for  the 
temperature  in  Column  3  of  the  tables  of  the  properties  of  saturated 
steam. 


6    0 


1COO 


800 


QUANTITY  OF   HEAT  IN  BRITISH  THERMAL  UNITS 

FIG.  119. — Diagram  of  steam-generation. 


132  STEAM  ABOVE  ATMOSPHERIC   PRESSURE 

For  example: 


(1)  .     .     At  100  pounds  absolute,  |/px  2.036  =  ^203.6. 

As  the  sixth  root  is  the  cube  root  of  the  square  root  of  the  number, 
then  1/203.6  =  14.2688,  and  the  1/14.2688  =  2.42516  X  176.4  =  427.7  - 
100  =  327.6°,  as  in  Column  3. 

The  specific  heat  of  water  (which  has  been  assigned  as  0),  at  the 
zero  of  absolute  pressure  and  32°  F.  of  temperature,  gradually  in- 
creases in  its  heat-unit  quantity,  equivalent  to  its  thermometric 
temperature,  so  that  at  212°  it  has  absorbed  180.5  heat-units  per 
pound  to  raise  its  temperature  from  32°  to  212°  F.,  with  an  increasing 
ratio  throughout  the  range  of  pressures  and  temperatures  in  use. 
The  formula  for  the  specific  heat  of  water  as  given  by  Regnault  and 
Rankine  for  any  temperature  T,  above  32°  F.,  is 

(2)  .     ,    T-32°+0.000,000,103x[(T-39.1)3  +  (7.1)3]  =  the  number 
of  heat-units  imparted  to  the  water  as  represented  in  Column  4,  Table 
XX,  of  the  properties  of  saturated  steam. 

The  latent  heat  of  vaporization  of  water,  Column  5  in  the  steam 
table,  is  from  Rankine's  formula : 

(3)  .     .     L  =  l,091.7-(.698(t-32°),  in  which  t  =  the  thermometric 
temperature  in  Column  3. 

The  total  amount  of  heat  in  steam,  as  in  Column  6,  consists  of  the 
amounts  in  Columns  4  and  5  added,  and  may  be  computed  from  the 
formula  of 'Regnault,  in  which 

(4)  .     .     H  =  1,091.7  +  (.305(t-  32°),  t  being  the  thermometric  tem- 
perature in  Column  3.     For  example: 

212° - 32°  =  180 X. 305  =  54.9,  and  54.9  +  1,091.7  =  1,146.6,  as  in 
Column  6  of  the  table  of  properties  of  saturated  steam.  The  specific 
heat  of  steam  is  uniform  throughout  the  range  of  temperatures  in 
contact  with  its  water  of  generation,  and  is  assigned  as  0.305 
(water  1). 

The  specific  heat  of  steam  may  also  be  used  for  obtaining  the 
heat-unit  values  in  Column  6,  Table  XX.  The  latent  heat  of  steam 
at  zero  pressure  is  1,082  heat-units;  then  the  temperature  due  to  the 
absolute  pressure  multiplied  by  the  specific  heat,  plus  1,082,  equals 
the  total  units  above  32°  F. 


UNIVERSITY 


STEAM  ABOVE  ATMOSPHERIC   PRESSURE  133 

For  example:  (212°  X.  305)  +  1,082  =  1,146.6  heat-units,  as  in  Col- 
umn 6;  also  at  100.3  gauge-pressure  =  115  absolute,  the  temperature 
in  Column  3:  (337.9  X.  305)  +  1,082  =  1,185.05,  and  so  on. 

Steam  has  its  critical  temperature  at  about  2,052°  absolute 
(1,592°  F.),  above  which  the  latent  heat  of  evaporation  will  be  zero  and 
there  would  be  no  difference  between  the  liquid  and  vaporous  forms, 
as  its  liquid  volume  will  have  disappeared. 

The  values  in  Columns  7,  8,  and  9  are  relative,  so  that 

-     Column  9  ,     .  -,  ,     r  •  •    *     ,% 

Column  7  =  —  (weight  of  water  per  cubic  foot)  ; 


Column  8  =  —  -  —  ,  and  Column  9  = 


Column  7  Column  8 

The  volume  of  steam  per  pound  of  water  at  any  temperature  may 
be  obtained  from  the  formula: 

He 

(5)     ....     V2  =  V 


...      v2=  vi  -i-  ^ 

-~  t,  in  which  He  =  the  foot-pound  value 
d.t 

of  the  latent  heajb  in  Column  5;  ¥2  =  the  volume  of  saturated  steam 
in  cubic  feet;  t  =  absolute  temperature  of  water  and  steam;  dp  =  dif- 
ferential pressure  per  square  foot;  dt  =  differential  temperature  or 
1°  F.;  Vi=  volume  of  water  at  temperature  t. 

The  difference  in  pressure  per  degree  F.,  at  atmospheric  pressure  for  1 

dp     2945 
heat-unit,  is  ~rr  =  ~~j — X 144  =  42.408  pounds  per  square  foot;  then 

as  water  increases  in  volume  .04775  per  unit  of  heat  from  its  maxi- 
mum density  (39.1°  F.),  its  volume  per  pound  is  therefore  - 


0.01602  cubic  foot.     Then  0.01602  X  1.04775  =  0.01678,  its  increased 
volume  for  1  heat-unit. 

The  cubic  feet  of  steam  per  pound  of  water  at  atmospheric  pres- 
sure may  be  computed  from  the  following  formula : 

(6)     .     .    0.01678  + Jg|gg=26.37,  as  in  Column  7. 


134  STEAM  ABOVE  ATMOSPHERIC   PRESSURE 

For  30  pounds  absolute  pressure  the  difference  in  temperature  per 
pound  of  pressure  from  Column  3  is 

(7)     .     .     1.886°  F.  and  -—  ^—  =  .5302  X  144  =  76.35,  the  ratio. 

l.oob 


in  Column  7. 

For  100  pounds  absolute  the  ratio  will  be  —  =  1.43X144  =  205.9. 


(8)     .     .     Then  0.01678  +  =  4.227  +  .017  =  4.244. 


Again,  for  200  pounds  absolute,  the  ratio   of   pressure   to  dif- 
ferential   temperature    is  —  =2.44x144  =  351.3. 


. 
(9)     .     .     Then    0.01678  +  =  2.217  +0.017  =  2.234,    the 


cutting  off  of  fractions  making  a  slight  discrepancy  from  the  tables 
as  established. 

The  total  heat-units  in  Column  6  may  be  obtained  directly  from 
the  temperature  in  Column  3  by  the  formula 

(10)  .     .     1,091.7  +  .305  (Column  3)  -32,  in  which  1,091.7  is  the 
total  value  in  heat-units  of  the  vapor  of  water  at  the  absolute  zero 
of  pressure,  and  .305  the  specific  heat  of  saturated  steam. 

Then,  for  example,  at  100  pounds  absolute  pressure,  from  the 
temperature  in  Column  3,  we  have, 

(11)  .     .     327.6  -  32  =  295.6  X.  305  =  90.15  +  1,091.7  =  1,181.85,  as 
in  Column  6. 


STEAM  ABOVE  ATMOSPHERIC   PRESSURE 


135 


TABLE    XX. — PROPERTIES    OF    SATURATED    STEAM — PRESSURES,  TEMPERATURE, 

VOLUME,  WEIGHT,  ETC. 


if- 

*& 

||| 

!*'  ^ 

||| 

IV. 

01  c  oj 

y 

2s, 

j| 

IB 

IW 

Pi 

|JS 

S§"£ 

ft 

*  j 

III 

* 

2 

3 

4 

5 

6 

7 

8 

9 

2.035 

1 

102.0° 

70.0 

1,043.0 

1,113.0 

330.4 

.00303 

20.628 

4.07 

2 

126.3 

94.4 

1,026.1 

1,120.5 

171.9 

.00582 

10,730 

6.105 

3 

141.7 

109.8 

1,015.4 

1,125.2 

117.8 

.00852 

7,325 

8.14 

4 

153.1 

121.3 

1,007.4 

1,128.7 

89.51 

.01117 

5,588 

10.175 

5 

162.4 

130.6 

1,000.9 

1,131.5 

72.56 

.01378 

4,530 

12.21 

6 

170.2 

138.4 

995.4 

1,133.8 

61.14 

.01636 

3,816 

14.245 

7 

176.9 

145.2 

990.7 

1,135.9 

52.89 

.01891 

3,302 

16.28 

8 

183.0 

151.3 

986.5 

1,137.8 

46.65 

.02144 

2,912 

18.315 

9 

188.4 

156.7 

982.7 

1,139.4 

41.77 

.02394 

2,607 

20.35 

10 

193.3 

161.7 

979.3 

1,141.0 

37.83 

.02644 

2,361 

22.385 

11 

197.8 

166.2 

976.1 

1,142.3 

34.59 

.02891 

2,151 

24.42 

12 

202.0 

170.5 

973.1 

1,143.6 

31.87 

.03138 

1,990 

26.455 

13 

205.9 

174.4 

970.4 

1,144.8 

29.56 

.03383 

1,845 

28.49 

14 

209.6 

178.1 

967.8 

1,145.9 

27.58 

.03626 

1,721 

29.92 

14.7 

212.0 

180.5 

966.1 

1,146.6 

26.37 

.03793 

1,646 

.      .3 

15 

213.1 

181.6 

965.3 

1,146.9 

25.85 

.03869 

,614 

&  1.3 

16 

216.3 

184.9 

963.0 

1,147.9 

24.33 

.04111 

,519 

i  2.3 

17 

219.5 

188.1 

960.8 

1,148.9 

22.98 

.04352 

,434 

0  3.3 

18 

222  4 

191.1 

958.8 

1,149.9 

21.78 

.04592 

,359 

4.3 

19 

225!  3 

193.9 

956.7 

1,150.6 

20.70 

.04831 

,292 

5.3 

20 

228.0 

196.7 

954.8 

1,151.5 

19.73 

.05070 

,281 

6.3 

21 

230.6 

199.3 

952.9 

1,152.2 

18.84 

.05307 

,176 

7.3 

22 

233.1 

201.8 

951  .2 

1,153.0 

18.04 

.05545 

,126 

8.3 

23 

235.5 

204.3 

949.5 

1,153.8 

17.30 

.05781 

,080 

9.3 

24 

237.8 

206.6 

947.8 

1,154.4 

16.62 

.06017 

1,038 

10.3 

25 

240.1 

208.9 

946.3 

1,155.2 

16.00 

.06252 

998.4 

11.3 

26 

242.2 

211.1 

944.8 

1,155.9 

15.42 

.06487 

962.3 

12.3 

27 

244^3 

213.2 

943.2 

1,156.4 

14.88 

.06721 

928.8 

13.3 

28 

246.4 

215.3 

941.8 

1,157.1 

14.38 

.06955 

897.6 

14.3 

29 

248.4 

217.3 

940.4 

1,157.7 

13.91 

.07188 

868.5 

15.3 

30 

250.3 

219.3 

939.0 

1,158.3 

13.48 

.07420 

841.3 

16.3 

31 

252.2 

221.2 

937.7 

1,158.9 

13.07 

.07652 

815.8 

17.3 

32 

254.0 

223.0 

936.4 

1,159.4 

12.68 

.07884 

791.8 

18.3 

33 

255.8 

224.8 

935.1 

1,159.9 

12.32 

.08115 

769.2 

19.3 

34 

257.5 

226.6 

933.9 

1,160.5 

11.98 

.08346 

748.0 

20.3 

35 

259.2 

228.3 

932.7 

1,161.0 

11.66 

.08577 

727.9 

21.3 

36 

260.9 

230.0 

931.5 

1,161.5 

11.36 

.08807 

708.8 

22.3 

37 

262.5 

231.7 

930.4 

1,162.1 

11.07 

.09036 

690.8 

23.3 

38 

264.1 

233.3 

929.3 

1,162.6 

10.79 

.09266 

673.7 

24.3 

39 

265.6 

234.8 

928.1 

1,162.9 

10.53 

.09495 

657.5 

25.3 

40 

267.2 

236.4 

927.0 

1,163.4 

10.28 

.09723 

642.0 

26.3 

41 

268.7 

237.9 

926.0 

1,163.9 

10.05 

.09951 

627.3 

27.3 

42 

270.1 

239.4 

924.9 

1,164.3 

9.826 

.  10179 

613.3 

28.3 

43 

271.6 

240.8 

923.9 

1,164.7 

9.609 

.  10407 

599.9 

29.3 

44 

273.0 

242.3 

922.0 

1,165.2 

9.403 

.10635 

587.0 

30.3 

45 

274.3 

243.7 

921.9 

1,165.6 

9.207 

.  10862 

574.7 

136 


STEAM  ABOVE  ATMOSPHERIC   PRESSURE 


TABLE    XX. — PROPERTIES    OF    SATURATED    STEAM — PRESSURES,   TEMPERATURE, 
VOLUME,  WEIGHT,  ETC. — (Continued.) 


Gauge 

pressure, 
pounds. 

Absolute 
pressure, 
pounds. 

Temperature 
of  water, 
Fahrenheit. 

Heat-units 
from  32°  F. 
to  temp., 
Column  3. 

Latent  heat 
of  vaporiza- 
tion, units. 

O>  c"?~  . 

^ST^ 

P"1 

111 

III 

°rH  3 

>'H  0 

Weight  of 
1  cubic 
foot  of  steam. 

Relative 
volume  to 
water. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

31.3 

46 

275.7° 

245.1 

920.9 

,166.0 

9.018 

.11088 

563.0 

32.3 

47 

277.0 

246.4 

920.0 

,166.4 

8.838 

.11315 

551.7 

33.3 

48 

278.3 

247.8 

919.1 

,166.9 

8.665 

.11541 

540.9 

34.3 

49 

279.6 

249.1 

918.1 

,167.2 

8.498 

.11767 

530.5 

35.3 

50 

280.9 

250.4 

917.3 

,167.7 

8.338 

.11993 

520.5 

36.3 

51 

282.2 

251.6 

916.4 

,168.0 

8.185 

.12218 

510.9 

37.3 

52 

283.4 

252.9 

915.5 

,168.4 

8.037 

.  12443 

501.7 

38.3 

53 

284.6 

254.1 

914.7 

,168.8 

7.894 

.  12668 

492.8 

39.3 

54 

285.8 

255.3 

913.8 

,169.1 

7.756 

.  12893 

484.2 

40.3 

55 

287.0 

256.5 

912.9 

,169.4 

7.624 

.13112 

475.9 

41.3 

56 

288.1 

257.7 

912.1 

,169.8 

7.496 

.13341 

467.9 

42.3 

57 

289.3 

258.9 

911.3 

,170.2 

7.372 

.  13565 

460.2 

43.3 

58 

290.4 

260.0 

910.5 

1,170.5 

7.252 

.13789 

452.7 

44.3 

59 

291.5 

261.1 

909.7 

1,170.8 

7.136 

.14013 

445.5 

45.3 

60 

292.6 

262.2 

908.9 

1,171.1 

7.024 

.  14236 

438.5 

46.3 

61 

293.7 

263.3 

908.2 

1,171.5 

6.916 

.  14459 

431.7 

47.3 

62 

294.7 

264.4 

907.4 

1,171.8 

6.811 

.  14682 

425.2 

48.3 

63 

295.8 

265.5 

906.6 

,172.1 

6.709 

.  14905 

418.8 

49.3 

64 

296.8 

266.6 

905.9 

,172.5 

6.610 

.15128 

412.6 

50.3 

65 

297.8 

267.6 

905.2 

,172.8 

6.515 

.  15350 

406.6 

51.3 

66 

298.8 

268.6 

904.4 

,173.0 

6.422 

.  15572 

400.8 

52.3 

67 

299.8 

269.7 

903.7 

,173.4 

6.332 

.15794 

395.2 

53.3 

68 

300.8 

270.8 

903.0 

,173.7 

6.244 

.16016 

389.8 

54.3 

69 

301.8 

271.7 

902.3 

,174.0 

6.159 

.16237 

384.5 

55.3 

70 

302.8 

272.7 

901.6 

,174.3 

6.076 

.  16458 

379.3 

56.3 

71 

303.7 

273.6 

901.0 

,174.6 

5.995 

.  16679 

374.3 

57.3 

72 

304.7 

274.6 

900.2 

,174.8 

5.917 

.  16900 

369.4 

58.3 

73 

305.6 

275.6 

899.6 

,175.2 

5.841 

.17121 

364.6 

59.3 

74 

306.5 

276.5 

898.9 

,175.4 

5.767 

.  17342 

360.0 

60.3 

75 

307.4 

277.4 

898.3 

,175.7 

5.694 

.  17562 

355.5 

61.3 

76 

308.3 

278.4 

897.7 

,176.1 

5.624 

.17783 

351.1 

62.3 

77 

309.2 

279.3 

897.0 

,176.3 

5.555 

.  18003 

346.8 

63.3 

78 

310.1 

280.2 

896.4 

,176.6 

5.488 

.  18223 

342.6 

64.3 

79 

311.0 

281.1 

895.7 

,176.8 

5.422 

.  18443 

338.5 

65.3 

80 

311.9 

282.0 

895.1 

,177.1 

5.358 

.  18663 

334.5 

66.3 

81 

312.7 

282.8 

894.4 

,177.3 

5.296 

.18882 

330.6 

67.3 

82 

313.6 

283.7 

893.9 

,177.6 

5.235 

.19102 

326.8 

68.3 

83 

314.4 

284.6 

893.3 

,177.9 

5.176 

.  19321 

323.1 

69.3 

84 

315.3 

285.4 

892.7 

,178.1 

5.118 

.  19540 

319.5 

70.3 

85 

316.1 

286.3 

892.1 

,178.4 

5.061 

.  19759 

315.9 

71.3 

86 

316.9 

287.1 

891.5 

,178.6 

5.006 

.  19978 

312.5 

72.3 

87 

317.7 

287.9 

891.0 

,178.9 

4.951 

.20197 

309.1 

73.3 

88 

318.5 

288.8 

890.3 

,179.1 

4.898 

.20416 

305.8 

74.3 

89 

319.3 

289.6 

889.8 

,179.4 

4.846 

.20634 

302.5 

75.3 

90 

320.1 

290.4 

889.2 

,179.6 

4.796 

.20853 

299.4 

STEAM  ABOVE  ATMOSPHERIC   PRESSURE 


137 


TABLE    XX. — PROPERTIES     OF     SATURATED  STEAM — PRESSURES,  TEMPERATURE, 
VOLUME,  WEIGHT,  ETC. — (Continued.) 


0  .r    . 

3  .  -s! 

5^   r» 

1§5 

^ 

"o   -•* 

•s  3 

eS 

s§| 

l|! 

2  *i 
Hi 

<  a  & 

Temperat 
of  water 
Fahrenhe 

Heat-uni 
from  32° 
to  temr 
Column 

Jfl 

III 

|Jl'l 

*C   03 

»  G% 

jii 

ill 

•S^S 

n 

Relativi 
volume  1 
water. 

i 

2 

3 

4 

5 

6 

7- 

8 

9 

76.3 

91 

320.9° 

291.2 

888.7 

1.179.9 

4.746 

.21071 

296.3 

77.3 

92 

321.7 

292.0 

888.1 

1,180.1 

4.697 

.21289 

293.2 

78.3 

93 

322.4 

292.8 

887.6 

1,180.4 

4.650 

.21507 

290.2 

79.3 

94 

323.2 

293.5 

887.0 

1,180.5 

4.603 

.21725 

287.3 

80.3 

95 

323.9 

294.3 

886.4 

1,180.7 

4.557 

.21943 

284.5 

81.3 

96 

324.7 

295.1 

885.9 

,181.0 

4.513 

.22160 

281.7 

82.3 

97 

325.4 

295.8 

885.3 

,181.2 

4.469 

.22378 

279.0 

83.3 

98 

326.2 

296.6 

884.8 

,181.4 

4.426 

.22595 

276.3 

84.3 

99 

326.9 

297.4 

884.3 

,181.7 

4.384 

.22812 

273.7 

85.3 

100 

327.6 

298.1 

883.8 

,181.9 

4.342 

.23029 

271.1 

86.3 

101 

328.3 

298.8 

883.2 

1,182.0 

4.302 

.23246 

268.5 

87.3 

102 

329.1 

299.6 

882.8 

1,182.3 

4.262 

.23463 

266.0 

88.3 

103 

329.8 

300.3 

882.2 

1,182.5 

4.223 

.23680 

263.6 

89.3 

104 

330.5 

301.0 

881.7 

1,182.7 

4.185 

.23897 

261.2 

90.3 

105 

331.2 

301.7 

881.2 

1,182.9 

4.147 

.24114 

258.9 

91.3 

106 

331.9 

302.4 

880.7 

1,183.1 

4.110 

.24330 

256.6 

92.3 

107 

332.6 

303.2 

880.3 

1,183.5 

4.074 

.24547 

254.8 

93.3 

108 

333.2 

303.9 

879.7 

1,183.6 

4.038 

.24763 

252.1 

94.3 

109 

333.9 

304.6 

879.2 

1,183.8 

4.003 

.24979 

249.9 

95.3 

110 

334.6 

305.2 

878.8 

1,184.0 

3.969 

.25195 

247.8 

96.3 

111 

335.3 

305.9 

878.3 

1,184.2 

3.935 

.25411 

245.7 

97.3 

112 

335.9 

306.6 

877.7 

1,184.3 

3.902 

.25626 

243.6 

98.3 

113 

336.6 

307.3 

877.3 

1,184.6 

3.870 

.25842 

241.6 

99.3 

114 

337.2 

308.0 

876.8 

1,184.8 

3.838 

.26058 

239.6 

100.3 

115 

337.9 

308.6 

876.4 

1,185.0 

3.806 

.26273 

237.6 

101.3 

116 

338.5 

309.3 

875.9 

1,185.2 

3.775 

.26489 

235.7 

102.3 

117 

339.2 

309.9 

875.4 

1,185.3 

3.745 

.26704 

233.8 

103.3 

118 

339.8 

310.6 

875.0 

1,185.6 

3.715 

.26920 

231.9 

104.3 

119 

340.4 

311.2 

874.5 

1,185.7 

3.685 

.27135 

230.1 

105.3 

120 

341.1 

311.9 

874.0 

1,185.9 

3.656 

.27350 

228.3 

106.3 

121 

341.7 

312.5 

873.7 

1,186.2 

3.628 

.27565 

226.5 

107.3 

122 

342.3 

313.2 

873.2 

1,186.4 

3.600 

.27780 

224.7 

108.3 

123 

342.9 

313.8 

872.7 

1,186.5 

3.572 

.27995 

223.0 

109.3 

124 

343.5 

314.4 

872.3 

1,186.7 

3.545 

.28210 

221.3 

110.3 

125 

344.1 

315.1 

871.8 

1,186.9 

3.518 

.28424 

219.6 

111.3 

126 

344.7 

315.7 

871.4 

1,187.1 

3.492 

.28639 

218.0 

112.3 

127 

345.3 

316.3 

871.0 

1,187.3 

3.466 

.28853 

216.4 

113.3 

128 

345.9 

316.9 

870.5 

1,187.4 

3.440 

.29068 

214.8 

114.3 

129 

346.5 

317.5 

870.0 

1,187.6 

3.415 

.29282 

213.2 

115.3 

130 

347.1 

318.1 

869.5 

1,187.8 

3.390 

.29496 

211.6 

116.3 

131 

347.6 

318.7 

868.9 

1,188.0 

3.370 

.29700 

210.1 

117.3 

132 

348.2 

319.3 

868.3 

1,188.2 

3.355 

.29900 

208.6 

118.3 

133 

348.8 

319.9 

867.9 

1,188.3 

3.340 

.30060 

207.1 

•   119.3 

134 

349.4 

320.6 

867.5 

1,188.5 

3.328 

.30220 

205.7 

120.3 

135 

350.0 

321.3 

867.0 

1,188.7 

3.304 

.30580 

204.2 

138 


STEAM  ABOVE  ATMOSPHERIC   PRESSURE 


TABLE    XX. — PROPERTIES    OF    SATURATED   STEAM — PRESSURES,   TEMPERATURE, 
VOLUME,  WEIGHT,  ETC. — (Continued.) 


£   ^ 

«*-     8 

Ill 

III 

Q  HJ  C 

in 

fe  oj  C 

fifi  MI 

jfe 

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2 

3 

4 

5 

6 

7 

8 

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121.3 

136 

350.5° 

321.9 

867.6 

1,188.9 

3.280 

.30840 

202.8 

122.3 

137 

351.1 

322.5 

867.1 

1,189.0 

3.260 

.31045 

201.4 

123.3 

138 

351.8 

323.1 

866.6 

1,189.2 

3.240 

.31292 

200.0 

124.3 

139 

352.2 

323.7 

866.1 

1,189.4 

3.220 

.31313 

198.7 

125.3 

140 

352.8 

324.3 

865.6 

1,189.6 

3.201 

.31534 

197.3 

126.3 

141 

353.3 

325.0 

865.1 

1,189.7 

3.182 

.31752 

196.0 

127.3 

142 

353.9 

325.7 

864.5 

1,189.9 

3.163 

.31950 

194.7 

128.3 

143 

354.4 

326.3 

863.9 

1,190.0 

3.144 

.32110 

193.4 

129.3 

144 

355.0 

327.1 

863.2 

1,190.2 

3.123 

.32320 

192.2 

130.3 

145 

355.5 

327.8 

862.6 

1,190.4 

3.101 

.32530 

190.9 

131.3 

146 

356.0 

328.4 

862.2 

1,190.5 

3.067 

.3274 

189.7 

132.3 

147 

356.6 

328.9 

861.8 

1,190.7 

3.050 

.3295 

188.5 

133.3 

148 

357.1 

329.5 

861.4 

1,190.9 

3.03 

.3316 

187.3 

134.3 

149 

357.6 

330.0 

861.0 

1,191.0 

3.01 

.3337 

186.1 

135.3 

150 

358.2 

330.6 

860.6 

1,191.2 

2.99 

.3358 

184.9 

136.3 

151 

358.7 

331.1 

860.2 

1,191.3 

2.97 

.3379 

183.7 

137.3 

152 

359.2 

331.6 

859.9 

1,191.5 

2.95 

.3400 

182.6 

138.3 

153 

359.7 

332.2 

859.5 

1,191.7 

2.93 

.3421 

181.5 

139.3 

154 

360.2 

332.7 

859.1 

1,191.8 

2.91 

.3442 

180.4 

140.3 

155 

360.7 

333.2 

858.7 

1,192.0 

2.89 

.3463 

179.2 

141.3 

156 

361.1 

333.8 

858.4 

1.192.1 

2.87 

.3483 

178.1 

142.3 

157 

361.8 

334.3 

858.0 

M92.  3 

2.85 

.3504 

177.0 

143.3 

158 

362.3 

334.8 

857.6 

1,192.4 

2.84 

.3525 

176.0 

144.3 

159 

362.8 

335.3 

857.2 

1,192.6 

2.82 

.3546 

174.9 

145.3 

160 

363.3 

335.9 

856.9 

1,192.7 

2.80 

.3567 

173.9 

146.3 

161 

363.8 

336.4 

856.5 

1,192.9 

2.79 

.3588 

172.9 

147.3 

162 

364.3 

336.9 

856.1 

1,193.0 

2.77 

.3609 

171.9 

148.3 

163 

364.8 

337.4 

855.8 

1,193.2 

2.76 

.3630 

171.0 

149.3 

164 

365.3 

337.9 

855.4 

1,193.3 

2.74 

.3650 

170.0 

150.3 

165 

365.7 

338.4 

855.1 

1,193.5 

2.72 

.3671 

169.0 

151.3 

166 

366.2 

338.9 

854.7 

1,193.6 

2.71 

.3692 

168.1 

152.3 

167 

366.7 

339.4 

854.4 

1,193.8 

2.69 

.3713 

167.1 

153.3 

168 

367.2 

339.9 

854.0 

1,193.9 

2.68 

.3734 

166.2 

154.3 

169 

367.7 

340.4 

853.6 

1,194.1 

2.66 

.3754 

165.3 

155.3 

170 

368.2 

340.9 

853.3 

1,194.2 

2.65 

.3775 

164.3 

156.3 

171 

368.6 

341.4 

852.9 

1,194.4 

2.63 

.3796 

163.4 

157.3 

172 

369.1 

341.9 

852.6 

1,194.5 

2.62 

.3817 

162.5 

158.3 

173 

369.6 

342.4 

852.3 

1,194.7 

2.61 

.3838 

161.6 

159.3 

174 

370.0 

342.9 

851.9 

1,194.8 

2.59 

.3858 

160.7 

160.3 

175 

370.5 

343.4 

851.6 

1,194.9 

2.58 

.3879 

159.8 

161.3 

176 

371.0 

343.9 

851.2 

1,195.1 

2.56 

.3900 

158.9 

162.3 

177 

371.4 

344.3 

850.9 

1,195.2 

2.55 

.3921 

158.1 

163.3 

178 

371.9 

344.8 

850.5 

1,195.4 

2.54 

.3942 

157.2 

164.3 

179 

372  A 

345.3 

850.2 

1,195.5 

2.52 

.3962 

156.4 

165-3 

180 

372.8 

345.8 

849.9 

1,195.7 

2.51 

.3983 

155.6 

STEAM  ABOVE  ATMOSPHERIC  PRESSURE 


139 


TABLE  XX. — PROPERTIES     OF    SATURATED   STEAM — PRESSURES,  TEMPERATURE, 
VOLUME,  WEIGHT,  ETC. — (Continued.) 


Gauge 
pressure, 
pounds. 

Absolute 
pressure, 
pounds. 

Temperature 
of  water, 
Fahrenheit. 

Heat-units 
from  32°  F. 
to  temp.. 
Column  3. 

Latent  heat 
of  vaporiza- 
tion, units. 

Total  heat, 
Columns 
4  and  5, 
units. 

Volume  of 
1  pound, 
cubic  feet. 

Weight  of 
1  cubic 
foot  of  steam. 

Relative 
volume  to 
water. 

1 

2 

3 

4 

5 

6 

7  - 

8 

9 

166.3 

181 

373.3° 

346.3 

849.5 

1,195.8 

2.50 

.4004 

154.8 

167.3 

182 

373.7 

346.7 

849.2 

,195.9 

2.48 

.4025 

154.0 

168.3 

183 

374.2 

347.2 

848.9 

,196.1 

2.47 

.4046 

153.2 

169.3 

184 

374.6 

347.7 

848.5 

,196.2 

2.46 

.4066 

152.4 

170.3 

185 

375.1 

348.1 

848.2 

,196.3 

2.45 

.4087 

151.6 

171.3 

186 

375.5 

348.6 

847.9 

,196.5 

2.43 

.4108 

150.8 

172.3 

187 

375.9 

349.1 

847.6 

,196.6 

2.42 

.4129 

150.0 

173.3 

188 

376.4 

349.5 

84^.2 

,196.7 

2.41 

.4150 

149.2 

174.3 

189 

376.9 

350.0 

846.9 

,196.9 

2.40 

.4170 

148.5 

175.3 

190 

377.3 

350.4 

846.6 

,197.0 

2.39 

.4191 

147.8 

176.3 

191 

377.7 

350.9 

846.3 

1,197.1 

2.37 

.4212 

147.0 

177.3 

192 

378.2 

351.3 

845.9 

1,197.3 

2.36 

.4233 

146.3 

178.3 

193 

378.6 

351.8 

845.6 

1,197.4 

2.35 

.4254 

145.6 

179.3 

194 

379.0 

352.2 

845.3 

1,197.5 

2.34 

.4275 

144.9 

180.3 

195 

379.5 

352.7 

845.0 

1,197.7 

2.33 

.4296 

144.2 

181.3 

196 

380.0 

353.1 

844.7 

1,197.8 

2.32 

.4317 

143.5 

182.3 

197 

380.3 

353.6 

844.4 

1,197.9 

2.31 

.4337 

142.8 

183.3 

198 

380.7 

354.0 

844.1 

1,198.1 

2.29 

.4358 

142.1 

184.3 

199 

381.2 

354.4 

843.7 

1,198.2 

2^28 

.4379 

141.4 

185.3 

200 

381.6 

354.9 

843.4 

1,198.3 

2.27 

.4400 

140.8 

190.3 

205 

383.7 

357.1 

841.9 

1,199.0 

2.22 

.4503 

137.5 

195.3 

210 

385.7 

359.2 

840.4 

,199.6 

2.17 

.4605 

134.5 

200.3 

215 

387.7 

361.3 

838.9 

,200.2 

2.12 

.4707 

131.5 

205.3 

220 

389.7 

362.2 

838.6 

,200.8 

2.06 

.4852 

128.7 

215.3 

230 

393.6 

366.2 

835.8 

,202.0 

1.98 

.5061 

123.3 

225.3 

240 

397.3 

370.0 

833.1 

,203.1 

1.90 

.5270 

118.5 

235.3 

250 

400.9 

373.8 

830.5 

,204.2 

1.83 

.5478 

114.0 

285.3 

300 

417.4 

390.9 

818.3 

,209.2 

1.535 

.6515 

95.8 

335.3 

350 

432.0 

406.3 

807.5 

,213.7 

1.325 

.7545 

'  82.7 

385.3 

400 

444.9 

419.8 

797.9 

,217.7 

1.167 

.8572 

72.8 

435.3  < 

450 

456.6 

432.2 

789.1 

,221.3 

1.042 

.9595 

65.1 

485.3 

500 

467.4 

443.5 

781.0 

,224.5 

.942 

1.062 

58.8 

535.3 

550 

477.5 

454.1 

773.5 

,227.6 

.859 

1.164 

53.6 

585.3 

600 

486.9 

464.2 

766.3 

,230.5 

.790 

1.266 

49.3 

635.3 

650 

495.7 

473.6 

759.6 

,233.2 

.731 

1.368 

45.6 

685.3 

700 

504.1 

482.4 

753.3 

,235.7 

.680 

1.470 

42.4 

735.3 

750 

512.1 

490.9 

747.2 

,238.0 

.636 

1.572 

39.6 

785.3 

800 

519.6 

498.9 

741  .4 

1,240.3 

.597 

1.674 

37.1 

835.3 

850 

526.8 

506.7 

735.8 

1,242.5 

.563 

1.776 

34.9 

885.3 

900 

533.7 

514.0 

730.6 

1,244.7 

.532 

1.878 

33.0 

935.3 

950 

540.3 

521.3 

725.4 

1,246.7 

.505 

1.980 

31.4 

985.3 

1,000 

546.8 

528.3 

720.3 

1,248.7 

.480 

2.082 

30.0 

CHAPTER    X 


FLOW   OF    STEAM    THROUGH    ORIFICES,    NOZLES,    AND    PIPES 

THE  flow  of  steam  from  an  orifice  into  a  vacuum  may  be  com- 
puted with  approximate  accuracy  by  the  formula: 
(12)     .     .     .     4/T  + 460.6X60.2,  or  the  square  root  of  the  absolute 
temperature  multiplied  by  60.2,  and  the  product  by  .54,  the  coefficient 
for  the  velocity  at  initial  density  for  an  orifice. 

For  example:  at  75  pounds  absolute  pressure,  60  pounds  gauge- 
pressure,  the  temperature  is  307.4,  and 

/307.4  +  460.6  =  V768  =  27.712X60.2  =  1,667  X. 54  =  899.7, 

velocity  of  steam  at  its  initial  density. 

Into  the  atmosphere,  steam  flows  through  a  thin  plate-orifice,  at 
its  initial  density  due  to  its  absolute  pressure,  with  a  velocity  of 
3.5953  4/height  in  feet  of  a  column  of  steam,  uniform  in  density, 
equal  to  its  weight  at  its  initial  pressure  per  square  foot.  The  height 
is  equal  to  the  volume  of  1  pound  of  steam,  as  in  Column  7,  Table 
XX,  of  the  properties  of  saturated  steam,  multiplied  by  144  square 
inches  in  1  square  foot.  For  example : 

For  100  pounds  absolute  pressure  it 
is  100  X  4.342  X 144  =  62,524.8  feet,  and 
1/62,524.8  =  250.7x3.5953  =  901.3  feet  per 
second. 

The  velocity  of  the  jet  of  steam  from 
an  orifice  or  nozle  is  increased  in  the  ratio 
of  1.624,  so  that  in  a  short  straight  nozle, 
Fig.  120,  of  from  two  to  two  and  one-half 
times  its  diameter  in  length,  with  good 
entrance-curves,  the  velocity  may  be  901 X  1.624  =  1,463  feet.  In  the 
expanding  nozles,  as  designed  for  steam-turbines  of  the  Delaval  class, 
a  much  higher  velocity  is  claimed. 

The  velocity  of  flow  of  steam  in  pipes  depends  upon  the  pressure- 
head,  which  is  the  height  in  feet  of  a  column  of  steam  of  a  uniform 

140 


FIG.  120. — Straight  nozle. 


FLOW  OF  STEAM  THROUGH  ORIFICES,  NOZLES,  AND  PIPES  141 

density  of  the  steam  at  the  entrance  of  the  pipe— the  length  and 
diameter  of  the  pipe  in  feet— a  fractional  exponent— and  the  head 
against  which  it  is  flowing  at  the  terminal. 

The  formula  much  in  use  for  steam  flowing  from  a  long  pipe  into 
the  atmosphere  is: 


(13) 


50  y  —  d  =  velocity  in  feet  per  second. 

JLi 


L  and  d=  length  and  diameter  of  the  pipe  in  feet  or  decimals 
of  a  foot  for  d. 

Then,  as  in  the  previous  example,  for  100  feet  in  length  of  a 
1-inch  pipe,  and  boiler-pressure  of  100  pounds  absolute,  85.3  gauge, 
the  height  h,  as  before  explained,  is  62,524.8,  and 


762  5^4  8  

V      ?IQQ'   X  .0833  =  4/70.6  =  8.402  X 50  =  400. 1  feet  per  second. 

The  acceleration  in  velocity  of  steam  by  its  expansive  effort  in 
passing  from  a  converging  section  to  and  through  a  diverging  section 
of  a  jet-nozle,  such  as  used  for  impulse  energy  in  steam-turbines, 


FIG.  121. — Steam-nozle. 


FIG.  122. — Expanding  nozle. 


is  due  to  its  expansive  volume  being  greater  than  the  increasing  area 
of  the  diverging  walls  of  the  nozle,  less  the  loss  by  cooling,  as  the 
expansion  is  adiabatic.  From  the  general  formula  /T  + 460. 6x60.2 
for  75  pounds  absolute  pressure,  the  velocity  at  initial  pressure  gives 
1,667  feet  per  second  in  the  throat  of  an  expanding  nozle.  Then 
the  relative  volumes  per  pound,  of  steam  at  75  pounds  and  atmos- 

26  37 

pheric  pressure,  is:  -    —  =  4.63;  and  if  the  relative  areas  of  the  ex- 
5.o9 

panding  nozle  are  as  1  to  2,  the  volume  at  the  mouth  of  the  nozle 


142  FLOW  OF  STEAM  THROUGH  ORIFICES,  NOZLES,  AND  PIPES 

4  63 
will  be:  -;—  =  2.315,  and  deducting  the  shrinkage  from  the  adiabatic 

expansion,  2.3151 3  =  1.78;   then  1,667x1.78  =  2,968  feet  per  second. 

Fig.  123  shows  the  diverging  forms  of  nozles  for  impact-wheels,  in 
which  the  angle  of  impact  should  be  as  near  20°  from  the  plane  of 
rotation  as  possible. 

It  is  claimed,  as  stated  by  D.  K.  Clark,  that  when  steam  flows 
from  a  nozle  of  the  best  form,  "the  velocity  does  not  increase  when 
flowing  into  a  resisting  medium  at  any  pressure  below  58  per  cent. 


FIG.  123. — Diverging  nozles. 


FIG.  124. — Nozle  of  best  form. 


of  the  initial  pressure."  Then  160  pounds  absolute  pressure  X 58 
per  cent.  =92.8  pounds  absolute,  the  lowest  resisting  pressure  at 
which  the  velocity  ceases  to  increase. 

4  6 
The  ratio  of  the  volumes  at  these  pressures  is:  -—  =  1.643.    Then, 

2.8 

using  the  temperature  formula  1/T  +  460.6X60.2  for  160  pounds 
absolute  pressure,  we  have 

28.7  X  60.2  =  1,727.7  X. 58  =  1,002x1.643  =  1,646  feet  per  second. 


Again  using  the  formula  3.5953  1/height,  we  have  160x2. 8x1 44 
64,512  feet,  and 


4/64,512  =  253.9x3.5953  =  912.8,  and  912.8x1.643  =  1,499  feet  per 
second. 

In  a  diverging  continuation  of  the  nozle,  as  used  for  steam-turbines 
of  the  Delaval  type,  the  acceleration  in  velocity  due  to  expansion, 
less  the  adiabatic  condition  of  expansion,  will  be  in  the  ratio  of  the 
expanding-nozle  areas  at  initial  and  terminal  ends.  Then  if  the  ratio 
is  1  to  2,  the  velocity  from  the  above  equation  should  be:  1,499x2  = 
2,998  feet  per  second. 


FLOW  OF  STEAM  THROUGH  ORIFICES,  NOZLES,  AND  PIPES   143 

A  formula  deduced  from  Professor  Rateau's  formula,  based  on 
the  area  of  the  entropy  diagram  for  the  velocity  of  steam  in  feet  per 
second,  is:  _ 


(14)     .     .     V  =  224|i-T2)         +  2     in  which 


224  =  |/2gx778. 

TI  =  absolute  initial  temperature  of  saturated  steam;  T2  =  absolute 
terminal  temperature  at,  say,  100+460.6°  F.;  r  =  latent  heat  of  vapor- 
ization at  temperature  TI,  as  in  Column  5  of  steam  table.  Then  from 
a  nozle  of  best  form  with  steam  expanding  from  an  initial  pressure  of 
160  pounds  absolute  into  a  vacuum  of  a  little  less  than  1  pound  ab- 
solute pressure,  or  28  inches  of  mercury,  at  which  pressure  the  absolute 
temperature  T2  =  100  +  460.  6  =  560.  6,  and  substituting  figures  for  the 
letters  in  the  formula,  we  have  for  160  pounds  absolute  : 


224 1/823.9-560.6/^^1+-^^^  =4,027,  the  velocity  in  feet  per 

second. 

The  following  table  has  been  computed  for  velocities  from  a 
pressure  of  160  pounds  absolute,  expanded  to  various  stages  of  lower 
pressure  by  Rateau's  formulas,  in  which  the  figures  in  the  tables  of 
properties  of  saturated  steam  were  used.  For  the  dryness  of  steam 
from  condensation,  1  =  dry  saturated  steam,  and  1  —  x  =  the  per- 
centage of  moisture  or  condensation  by  expansion. 

This  is  found  by  the  formula : 

(15)     .     .     . — (^~^ — ~+hy.  log.  •=! )  =x,  the  relative  amount 

of  dry  stearn  after  expansion,  in  which  T2  is  absolute  temperature 
after  expansion;  TI  absolute  initial  temperature;  1.  h.  Ti.2,  latent 
heat  of  vaporization,  as  in  Column  5,  steam  table  XX. 

For  example,  substituting  the  values  for  expansion  from  160 
pounds  absolute  to  atmospheric  pressure,  we  have: 

672.6/856.9.,      ,       824.2\          as  in  Table  XXI. 


For  the  area  of  a  nozle  of  best  form,  as  in  Column  9  of  Table 

x  144 
XXI,  the  formula  is :  -~y-  (Column 8),  multiplied  by  the  square  inches 

in  a  foot,  and  the  product  divided  by  the  product  of  the  density  and 


144  FLOW  OF  STEAM  THROUGH  ORIFICES,  NOZLES,  AND  PIPES 

TABLE  XXI. — THEORETICAL  VELOCITY  AND  AREAS  OF  AN  EXPANDING  NOZLE  OF 
BEST  FORM  FOR  DRY  STEAM,  EXPANDED  FROM  160  POUNDS  ABSOLUTE  PRES- 
SURE PER  SQUARE  INCH  TO  LOWER  PRESSURES. 


Pressure 
absol'te, 
Ibs.  per 
sq.  in. 

T?1 
absolute 
degrees 

T'-T" 

degrees 

D, 

Ibs.  per 
cu.  ft. 

Vel., 
ft.  per 
sec. 

DV 

p 
P 

x, 

per  cent, 
dry. 

A,  area 
of  nozle, 
sq.  in. 

Profile 
of 
nozle. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

160 

823  9 

.3567 

1.000 

1.000 

2   31 

150 

818.8 

"d'.l 

.3358 

519 

174.2 

.937 

.992 

.818 

1.86 

140 

813.4 

10.5 

.3153 

745 

234.8 

.875 

.987 

.609 

1.38 

130 

807.7 

16.2 

.2949 

916 

270.1 

.812 

.982 

.524 

.21 

120 

801.7 

22.2 

.2735 

1,088 

297.5 

.750 

.975 

.472 

.09 

110 

795.2 

28.7 

.2519 

1,236 

311.3 

.687 

.969 

.448 

.03 

100 

788.2 

35.7 

.2303 

1,383 

318.5 

.625 

.963 

.444 

.02 

90 

780.7 

43.2 

.2085 

1,525 

317.9 

.562 

.957 

.433 

.00 

70 

763.4 

60.5 

.1645 

1,813 

298.3 

.437 

.942 

.454 

.04 

50 

741.5 

82.4 

.1199 

2,129 

255.1 

.312 

.923 

.521 

.20 

30 

710.9 

113.0 

.0742 

2,525 

187.3 

,187 

.894 

.740 

.70 

15 

673.7 

150.2 

.0386 

2,934 

112.9 

.094 

.865 

1.103 

2.54 

5 

623.0 

200.9 

.0137 

3.412 

47.3 

.031 

.817 

2.489 

5.72 

2 

586.9 

237.0 

.0058 

3,752 

21.7 

.012 

.786 

5.202 

12.01 

1 

562.6 

261.3 

.00303 

4,027 

12.2 

.006 

.769 

9.07 

20.94 

velocity  in  Column  6.     The  weight  of  steam  discharged  per  second 

DV 

per  square  inch  of  area  will  be : in  pounds. 

x  144 

The  proportional  diameters  of  an  expanding  nozle  for  the  theo- 
retical expansion  of  steam,  from  160  pounds  absolute,  is  given  in  Column 
10,  and  its  form  shown  in  Fig.  125,  which  is  a  profile  of  an  expanding 


.1          .2          .3          .4         .5         .6         .7         .8         .9        1.0 

FIG.  125. — Theoretical  curves  of  expanding  nozles. 

nozle  to  meet  the  conditions  of  velocity  and  expansion.  In  practice, 
the  expanding  part  of  the  nozle  is  much  reduced  in  order  to  increase  its 
velocity  by  reducing  the  lateral  expansion.  Fig.  125  shows  the  theo- 
retical profile  of  an  expanding  nozle  in  which  the  practical  lines  of  the 
expanding  part  are  shown  by  the  dotted  lines  as  used  for  turbine-nozles. 


FLOW  OF  STEAM  THROUGH  ORIFICES,  NOZLES,  AND  PIPES  145 


ENERGY     OF     STEAM 

The  theoretical  energy  of  steam  in  foot-pound  power  is  due  to  the 
difference  in  the  heat-unit  values  between  which  it  is  expanded, 
and  which,  multiplied  by  778,  the  foot-pound  value  per  heat-unit, 
equals  the  total  foot-pound  value  due  to  expansion  per  pound  of 
steam.  For  example:  the  heat-units  in  1  pound  of  steam  at  160 
pounds  absolute  are  1,192.7,  and  the  heat-unfts  in  1  pound  at 
atmospheric  pressure  are  966.1;  then,  1,192.7-966.1  =  226.6x778  = 

176  294 
176,294  foot-pounds,  and         '       =5.34  horse-power  per  pound  of 

oo,00u 

steam  per  minute. 

FLOW     OF     STEAM     THROUGH     LONG     PIPES 

The  weight  and  volume  of  steam  which  will  flow  through  a  pipe 
in  one  minute  from  a  given  pressure,  and  any  designated  loss  of 
pressure  from  friction,  may  be  obtained  from  the  following  general 
formula  for  the  flow  of  gases  and  vapors: 

(16)     .....     W-S 


W  =  total  weight  in  pounds,  which,  divided  by  the  weight  of  1  cubic 
foot  =  cubic  feet  per  minute;  D  =  density  or  weight  per  cubic  foot 
at  initial  pressure,  px;  p2  =  terminal  pressure  at  end  of  pipe;  d  = 
actual  diameter  of  the  pipe  in  inches;  L  =  length  of  pipe  in  feet. 

The  following  table  represents  the  weight  of  steam  that  will  flow 
per  minute  through  a  straight,  smooth  pipe  of  240  times  its  internal 
diameter,  with  a  loss  of  1  pound  in  the  pressure: 

For  sizes  of  pipe  less  than  6  inches,  the  flow  is  calculated  from 
the  actual  areas  of  "  standard"  pipe  of  such  nominal  diameters. 

For  horse-power,  multiply  the  figures  in  the  table  by  2.  For  any 
other  loss  of  pressure,  multiply  by  the  square  root  of  the  given  loss. 
For  any  other  length  of  pipe,  divide  240  by  the  given  length  expressed 
in  diameters,  and  multiply  the  figures  in  the  table  by  the  square  root  of 
this  quotient,  which  will  give  the  flow  for  1  pound  loss  of  pressure. 
Conversely,  dividing  the  given  length  by  240  will  give  the  loss  of 
pressure  for  the  flow  given  in  the  table. 


146  FLOW  OF  STEAM  THROUGH  ORIFICES,  NOZLES,  AND  PIPES 


TABLE  XXII. — FLOW  OF  STEAM  THROUGH  PIPES  OF  240  TIMES  THEIR  DIAMETER, 
WITH  A  Loss  OF  1  POUND  IN  PRESSURE. 


1  pressure  by 
.  Pounds  per 
uare  inch. 

Diameter  of  pipe  in  inches.                       Length  of  each  =  240  diameters. 

1 

u 

2 

2* 

3 

4 

5 

6 

8 

10 

12 

Sg 

Weight  of  steam  per  minute  in  pounds,  with  1  pound  loss  of  pressure. 

1 

2.07 

5.7 

10.27 

15.45 

25.38 

46.85 

77.3 

115.9 

211.4 

341.1 

502.4 

10 

2.57 

7.1 

12.72 

19.15 

31.45 

58.05 

95.8 

143.6 

262.0 

422.7 

622.5 

20 

3.02 

8.3 

14.94 

22.49 

36.94 

68.20 

112.6 

168.7 

307.8 

496.5 

731.3 

30 

3.40 

9.4 

16.84 

25.35 

41.63 

76.84 

126.9 

190.1 

346.8 

559.5 

824.1 

40 

3.74 

10.3 

18.51 

27.87 

45.77 

84.49 

139.5 

209.0 

381.3 

615.3 

906.0 

50 

4.04 

11.2 

20.01 

30.13 

49.48 

91.34 

150.8 

226.0 

412.2 

665.0 

979.5 

60 

4.32 

11.9 

21.38 

32.19 

52.87 

97.60 

161.1 

241.5 

440.5 

710.6 

1,046.7 

70 

4.58 

12.6 

22.65 

34.10 

56.00 

103.37 

170.7 

255.8 

466.5 

752.7 

1,108.5 

80 

4.82 

13.3 

23.82 

35.87 

58.91 

108.74 

179.5 

269.0 

490.7 

791.7 

1,166.1 

90 

5.04 

13.9 

24.92 

37.52 

61.62 

113.74 

187.8 

281.4 

513.3 

828.1 

1,219.8 

100 

5.25 

14.5 

25.96 

39.07 

64.18 

118.47 

195.6 

293.1 

534.6 

862.6 

1,270.1 

120 

5.63 

15.5 

27.85 

41.93 

68.87 

127.12 

209.9 

314.5 

573.7 

925.6 

1,363.3 

150 

6.14 

17.0 

30.37 

45.72 

75.09 

138.61 

228.8 

343.0 

625.5 

1,009.2 

1,486.5 

The  loss  of  head  due  to  the  friction  of  the  steam  entering  the  pipe, 
and  passing  elbows  and  valves,  will  reduce  the  flow  given  in  the  table. 
The  resistance  at  the  opening,  and  that  at  a  globe-valve,  are  each 
about  the  same  as  that  for  a  length  of  pipe  equal  to  114  diameters 
divided  by  a  number  represented  by  1  + (3. 6-=- diameter).  For  the 
sizes  of  pipes  given  in  the  table,  these  corresponding  lengths  are : 


1 

H 

2 

2& 

3 

4 

5 

6 

8 

10 

12 

25 

,j 

34 

41 

47 

52 

60 

66 

71 

79 

84 

88 

The  resistance  at  an  elbow  is  equal  to  two-thirds  that  of  a  globe- 
valve.  These  equivalents — for  opening,  for  elbows,  and  for  valves- 
must  be  added  in  each  instance  to  the  actual  length  of  pipe.  Thus  a 
4-inch  pipe,  120  diameters  (40  feet)  long,  with  a  globe-valve  and  three 
elbows,  would  be  equivalent  to  120  +  60  +  60  +  (3  X  40)  =  360  diameters 
long;  and  360 -=-240  =  1?.  It  would  therefore  have  IJjpounds  loss  of 
pressure  at  the  flow  given  in  the  table,  or  deliver  (1  -=-  \/\ \  =  .816)  =  81.6 
per  cent,  of  the  steam  with  the  same  (1  pound)  loss  of  pressure. 


CHAPTER    XI 

SUPERHEATED    STEAM    AND    ITS   WORK 

SATURATED  steam,  or  steam  which  has  exactly  the  temperature 
due  to  its  pressure,  has  aptly  been  described  as  steam  saturated  with 
heat,  and  the  chief  peculiarity  which  it  possesses  is  that  the  slightest 
abstraction  of  heat  is  followed  by  a  corresponding  condensation. 

Superheated  steam  is  generated  by  the  addition  of  heat  to  satu- 
rated steam.  The  behavior  of  superheated  steam  is  similar  to  that  of 
gases;  it  is  a  poor  conductor  of  heat,  and  has  the  special  peculiarity  of 
losing  a  certain  amount  of  heat  without  becoming  saturated  or  wet 
steam.  The  specific  heat  of  steam  is  only  0.48,  and  therefore  very 
little  heat  is  required  to  superheat  steam;  but  as  the  steam  loses 
the  heat  as  quickly  as  it  acquires  it,  every  passage  conveying  super- 
heated steam  should  be  well  covered  with  non-conducting  material. 
Although  there  are  some  losses  on  account  of  the  heat-radiation 
when  using  superheated  steam,  they  are  very  much  smaller  per  volume, 
because  the  loss  of  heat  from  superheated  steam  has  lower  calorific 
value  than  the  latent  heat  of  saturated  steam. 

The  economy  effected  by  using  superheated  steam  in  engines  is 
remarkable,  and,  acknowledging  this  fact,  a  great  number  of  steam- 
users  superheat  the  steam,  although  in  many  cases  only  a  few  degrees; 
yet  a  considerable  saving  in  steam  and  coal  is  always  the  result.  To 
obtain  the  full  benefit,  the  required  temperature  of  superheat  should 
be  600°  F.,  and  to  stand  this  temperature  the  engines  should  be 
specially  designed. 

The  use  of  highly  superheated  steam  does  not  require  high  boiler- 
pressures;  160  pounds  is  the  highest  to  be  recommended,  as  no  ad- 
vantage can  be  derived  by  exceeding  this.  As  the  amount  of  heat 
transmitted  from  the  steam  to  cylinder-walls,  and  vice  versa,  is 
much  lower  with  superheated  steam  than  with  saturated  steam,  the 
whole  range  of  temperature  from  boiler-pressure  to  vacuum  can  take 
place  in  two  cylinders,  so  that  the  use  of  a  triple-expansion  engine  does 

not  make  very  much  improvement  in  economy. 

147 


148  SUPERHEATED  STEAM  AND  ITS  WORK 

In  view  of  the  great  advantages  of  steam-superheating,  and  the 
great  number  of  engines  running  at  present  satisfactorily,  it  is  aston- 
ishing that  a  few  failures  have  caused  prejudices  among  some  engineers, 
who  make  the  general  introduction  of  the  use  of  superheated  steam 
very  difficult.  It  will  be  worth  mentioning  that  the  results  of  a  great 
number  of  trials  have  always  proved  a  great  saving  in  steam  and 
coal,  and  even  with  small  plants  and  simple  piston-valve  engines 
almost  the  same  good  economy  is  obtainable  as  with  large  engines 
with  most  exact  valve-gears.  It  is  therefore  recommended  that 
superheated  steam  should  be  used  in  connection  with  all  engines; 
the  only  question  to  be  settled  is  the  degree  of  superheat,  which 
largely  depends  on  local  circumstances  and  the  construction  of  the 
engine. 

Superheated-steam  engines  use  on  an  average  30  to  40  per  cent, 
less  steam  than  saturated-steam  engines  of  the  same  type.  Con- 
sequently boilers  can  be  made  30  per  cent,  smaller,  and  the  difference 
in  price  will  nearly  cover  the  cost  of  the  superheater.  For  the  same 
steam-consumption  the  superheated-steam 'engine  is  cheaper,  as  it 
may  be  worked  with  a  lower  boiler-pressure. 

One  of  the  most  troublesome  effects  of  expansion  is  found  in  the 
action  of  the  steam-valves.  Slide-valves  and  Corliss  valves  are  nat- 
urally affected  by  the  high  temperatures,  480  to  500°  F.  being  the 
upper  limit  for  the  latter.  Piston- valves,  when  carefully  constructed 
and  proportioned,  answer  well,  but  they  must  be  made  especially 
for  the  service.  The  longitudinal  expansion  of  the  cylinder  tends  to 
deform  the  steam-chest  and  valve-seat,  and  provision  must  be  made 
for  such  effects.  Rings  and  springs  in  valves  are  objectionable,  as 
it  is  difficult  to  keep  the  steam  from  getting  between  the  rings  and 
creating  increased  pressure  and  friction.  Poppet-valves  have  been 
used  with  much  success. 

The  adoption  of  superheated  steam  in  steam-engines  was  made 
possible  by  the  manufacture  of  heavy  mineral  oils  with  high-ignition 
points  and  by  the  now  common  practice  of  using  metallic  packing. 
From  a  purely  theoretical  point  of  view  the  advantage  gained  is  small, 
and  if  the  conditions  were  those  of  the  ideal  engine,  superheating  would 
never  have  been  heard  of.  On  entering  the  cylinder  of  a  steam-engine 
part  of  the  steam  is  condensed,  without  doing  any  work,  by  coming  in 
contact  with  the  walls  and  piston,  cooled  from  the  previous  exhaust- 


SUPERHEATED  STEAM  AND  ITS  WORK  149 

stroke.  This  reduces  the  working  value  of  the  steam  and  coats  the 
cylinder  with  a  film  of  water,  which  conducts  the  heat  much  more 
readily  to  the  cylinder-walls  than  in  the  case  of  dry  steam. 

The  principal  object  of  superheating  is  to  reduce  this  transfer  of 
heat  and  initial  condensation;  for  although  the  superheated  steam 
gives  up  some  of  its  heat  to  the  metal  on  admission,  there  is  no 
condensation,  the  only  effect  being  a  reduction  of  volume  and  a 
fall  in  temperature.  Superheating  also  tends  to~~prevent  leakage  at 
sliding  surfaces,  such  as  piston-rings,  valves,  etc.  No  matter  how 
tight  they  are  when  at  rest,  a  film  of  water,  creeping  along  between 
the  sliding  surfaces,  will  cause  steam  to  leak  through  when  the 
engine  is  running. 

At  300°  F.  of  superheat  the  volume  of  steam  is  increased  about 
50  per  cent.,  and  owing  to  this  increase  in  volume  less  heat  is  required 
to  produce  the  same  volume  for  superheated  steam  than  for  saturated 
steam  at  the  same  pressure.  Thus  less  heat  enters  the  cylinders  at 
each  stroke,  and  as  the  same  amount  of  heat  is  converted  into  work 
in  each  case,  the  economy  of  superheating  is  apparent. 

It  has  been  found  that  to  attain  a  certain  velocity  of  steam  in  a 
pipe,  superheated  steam  requires  a  smaller  drop  in  pressure  than 
saturated  steam  and,  as  less  steam  is  required  per  horse-power  when 
superheated,  a  reduction  may  be  made  in  the  size  of  the  piping, 
which  again  will  reduce  the  cost  as  well  as  the  loss  from  radiation. 

A  separator  will  be  unnecessary,  which  also  reduces  the  radiating 
surface;  and  the  absence  of  water  in  the  steam-pipes  does  away  with 
all  risk  of  getting  water  into  the  cylinders. 

The  superheater  may  have  three  different  positions  relative  to  the 
boiler:  1.  It  may  be  placed  in  the  flue  so  as  to  extract  heat  from  the 
gases  as  they  leave  the  boiler,  which  is  the  most  economical  method  of 
obtaining  superheat.  2.  It  may  be  placed  in  the  path  of  the  gases 
between  the  fire  and  the  boiler  proper.  3.  It  may  be  quite  separate, 
and  independently  fired. 

In  case  1,  a  good  boiler  should  take  up  enough  of  the  heat  from 
the  gases  to  allow  them  to  pass  out  at  a  temperature  but  little  above 
that  of  the  boiler.  If  only  a  low  degree  of  superheat  is  required,  this 
position  is  much  the  simplest  and  cheapest. 

Case  2  is  the  most  economical  method  from  point  of  view  of  fuel 
required,  but  the  difficulty  of  regulating  the  temperature  is  much 


150  SUPERHEATED  STEAM  AND  ITS  WORK 

greater.  In  Case  3  the  temperature  can  be  easily  regulated  and  the 
superheater  readily  cut  out  when  required.  It  is  a  more  wasteful 
method  than  either  of  the  other  two,  but  as  little  coal  is  required 
by  the  superheater  when  compared  with  the  boiler,  the  loss  does  not 
count  for  much. 

It  may  be  taken  as  a  general  rule  that  the  better  the  economy  of 
an  engine,  the  less  gain  there  will  be  from  superheat.  Thus  the  best 
results  should  be  looked  for  in  a  simple  engine  with  a  low  steam- 
pressure. 

The  question  of  the  cost  of  the  additional  heat  is  sometimes  raised, 
but  it  can  be  shown  that  much  less  heat  is  required  to  produce  a  cubic 
foot  of  superheated  steam  than  to  generate  a  cubic  foot  of  saturated 
steam  of  the  same  pressure. 

In  triple  and  quadruple  expansion  the  gain  is  small  unless  the 
superheating  is  carried  to  a  high  temperature.  It  varies,  of  course, 
with  the  point  of  cut-off  and  the  ratio  of  expansion. 

There  is  little  gain  due  to  superheating  in  any  cylinder  after  the 
stage  is  reached  in  which  the  steam  is  kept  dry  throughout  the  whole 
expansion,  the  only  object  of  taking  the  superheat  higher  is  to  obtain 
dry  steam  as  far  as  possible  during  the  whole  expansion  of  the  engine. 

The  same  effect  may  be  obtained  by  reheating  the  steam  in  the 
receivers  between  the  different  cylinders,  so  that  it  will  enter  each 
cylinder  superheated  sufficiently  to  insure  dryness  at  the  end  of  the 
stroke  in  that  cylinder.  This  can  be  effected  by  passing  the  super- 
heated steam  through  coils  in  the  receiver,  so  as  to  give  up  part  of  its 
heat  to  the  steam  that  has  already  expanded  in  the  previous  cylinder 
and  pass  on  to  the  steam-chest  of  the  engine  at  a  lower  degree  of 
superheat.  This  method  gives  the  advantage  of  a  high  degree  of 
superheat  without  the  disadvantage  of  extremely  high  temperature  in 
the  cylinders. 

The  effect  of  superheating  in  turbines  is  somewhat  different  from 
that  in  engines.  In  some  turbines  the  potential  energy  of  the  steam 
is  transformed  into  kinetic  energy  before  being  available  for  doing 
work.  This  is  effected  by  means  of  a  large  drop  of  pressure  through  a 
small  nozle.  Some  of  the  heat  appears  as  kinetic  energy,  and  if 
saturated  steam  were  used,  there  would  be  water  present  at  this 
pressure.  If  superheated,  the  extra  heat  in  the  steam  would  prevent 
any  condensation  and  increase  the  volume  and  velocity  of  the  steam. 


SUPERHEATED  STEAM  AND  ITS  WORK  151 

With  this  form  of  turbine  the  high-temperature  steam  never  comes  in 
contact  with  the  frictional  parts,  and  the  only  limit  to  the  degree  of 
superheat  is  apparently  the  temperature  at  which  the  strength  of  steel 
begins  to  be  affected.  Results  of  a  trial  have  been  published  on  a 
De  Laval  turbine  using  steam  at  930°  F.,  with  no  serious  difficulties 
encountered. 

The  ideal  efficiency  of  a  heat-engine  is  determined  by  the  range  of 
temperature  through  which  it  works  and  not  by  -the  medium  through 
which  that  heat  is  used.  This  theoretical  fact  is  employed  as  an  argu- 
ment in  favor  of  superheated  steam.  It  is  pretty  generally  recognized 
now  that  one  of  the  losses  of  the  steam-engine  is  the  interchange  of 
heat  which  goes  on  between  the  cylinder  metal  and  the  working  steam. 
To  prevent  this  interchange  it  is  usual  to  superheat  the  steam  so  that 
less  of  it  may  turn  into  water,  for  it  is  in  the  form  of  water  that  the 
working  fluid  exerts  its  worst  effects. 

Theorists  who  look  on  superheat  as  a  means  of  raising  the  tempera- 
ture of  the  working  fluid,  overlook  some  important  practical  considera- 
tions. During  the  period  of  time  that  the  admission-port  of  the 
cylinder  is  open,  the  piston  of  the  engine  is  pushed  forward  by  the 
pressure  of  the  steam  in  the  boiler.  The  steam  in  the  pipe  does  not 
expand.  It  flows  into  the  cylinder  in  obedience  to  the  push  which  it 
receives  from  behind,  and  this  push  is  not  even  due  in  all  cases  or 
entirely  to  expansion  in  the  boiler.  It  is  due  directly  to  the  heat  of 
the  fire,  which  causes  the  water  to  turn  into  steam.  It  is  this  bulk 
of  new  steam  that  pushes  the  engine-piston,  and  the  steam  between 
the  boiler  and  the  moving  face  of  the  piston  is  simply  a  strut;  for, 
.since  it  maintains  a  constant  pressure,  it  cannot  expand.  In  its 
passage  from  the  boiler  to  the  engine  through  a  superheater  it  re- 
ceives additional  heat  per  given  volume  of  saturated  steam,  and 
expands  to  a  new  volume,  due  to  the  amount  of  superheat,  without 
receiving  any  addition  of  water,  and  thereby  assumes  the  condition  of 
a  gas.  As  a  gas  it  does  work  by  expansion,  without  loss  from  con- 
densation, until  its  temperature  falls  to  the  saturation-point,  when 
its  further  expansion  assumes  the  condition  of  saturated  steam. 

Therefore  there  can  be  no  practical  economy,  considering  the 
heat-troubles  from  wear  and  tear,  by  using  superheat  at  a  greater 
temperature  than  will  insure  dry  steam  to  the  end  of  its  expansion- 
work. 


152 


SUPERHEATED  STEAM  AND  ITS  WORK 


TABLE  XXIII. — SPECIFIC  VOLUME  OF  SUPERHEATED  STEAM  IN  CUBIC  FEET  PER 
POUND  AT  TEMPERATURES  ABOVE  THAT  OF  SATURATED  STEAM. 


Absolute 
pressure. 

Saturated 
steam, 
volume. 

Specific  volume  for  degrees  of  superheat,  Fahrenheit. 

20° 

40° 

60° 

80° 

100° 

120° 

140° 

160° 

180° 

200° 

70 

6.14 

6.47 

6.64 

6.81 

6.98 

7.15 

7.32 

7.49 

7.66 

7.83 

8.00 

80 

5.42 

5.72 

5.88 

6.03 

6.17 

6.32 

6.47 

6.62 

6.77 

6.92 

7.07 

90 

4.86 

5.15 

5.28 

5.41 

5.54 

5.67 

5.81 

5.94 

6.07 

6.20 

6.33 

100 

4.04 

4.67 

4.79 

4.91 

5.03 

5.15 

5.27 

5.39 

5.51 

5.63 

5.75 

110 

4.03 

4.29 

4.42 

4.51 

4.61 

4.72 

4.83 

4.94 

5.05 

5.15 

5.26 

120 

3.71 

3.96 

4.06 

4.16 

4.26 

4.36 

4.46 

4.56 

4.66 

4.75 

4.85 

130 

3.44 

3.69 

3.78 

3.87 

3.96 

4.05 

4.14 

4.23 

4.32 

4.41 

4.51 

140 

3.21 

3.45 

3.53 

3.62 

3.69 

3.79 

3.87 

3.96 

4.05 

4.13 

4.20 

150 

3.01 

3.24 

3.32 

3.40 

3.48 

3.55 

3.63 

3.71 

3.79 

3.87 

3.95 

160 

2.83 

3.05 

3.13 

3.20 

3.28 

3.36 

3.42 

3.50 

3.57 

3.64 

3.72 

170 

2.67 

2.89 

2.96 

3.03 

3.10 

3.17 

3.24 

3.31 

3.38 

3.45 

3.52 

180 

2.53 

2.75 

2.81 

2.88 

2.94 

3.01 

3.07 

3.14 

3.21 

3.28 

3.34 

190 

2.41 

2.62 

2.68 

2.74 

2.80 

2.87 

2.93 

2.99 

3.05 

3.12 

3.18 

200 

2.29 

2.50 

2.56 

2.62 

2.68 

2.74 

2.80 

2.86 

2.91 

2.97 

3.03 

The  above  table  has  been  computed  by  Schmidt's  formula  based  on 
Hirns's  experiments,  namely: 

4.4.1  4_i_rr 
(17)     ......     Sv=0.59276x-    *       , 

in  which  Sv  =  specific  volume  in  cubic  feet  per  pound,  T  =  temperature 
of  saturated  steam  +  superheat,  P  =  absolute  pressure  in  pounds  per 
square  inch.  The  percentage  of  increase  in  volume  from  superheat,  apart 
from  its  freedom  from  condensation,  is  the  most  essential  factor  of  econ- 
omy from  the  use  of  superheat;  for  instance,  the  volume  of  saturated 

steam  at  160  pounds  is  2.83  cubic  feet  per  pound,  and  is  increased 

o  70 

by  200°  F.  superheat  to  3.72  cubic  feet  per  pound,  and  -^-  =  1.31, 

2.83 

or  31  per  cent,  increase  in  volume;  and  at  only  100°  of  superheat, 
which  may  be  saved  from  the  chimney-gases,  the  increase  in  volume 

Q      f)f\ 

is  ^jr  =  1.116,  or  over  11  per  cent. 

—  .      *  > 

The  following  table  represents  a  fair  approximation  to  ordinary 
practice,  but  does  not  meet  the  extraordinary  tests  that  have  been 
published  for  short  runs  with  superheat  reaching  near  or  quite  to  the 
temperature  of  incandescence.  Such  tests  may  make  a  good  showing, 
but  are  not  practicable  for  continued  service.  Mineral  oils  will  not 
give  the  required  service  at  temperatures  above  their  boiling-point. 


SUPERHEATED  STEAM  AND  ITS  WORK 


153 


AND  300°  F.,  FOR  VARIOUS 
INCH  VACUUM. 


27 


00°, 


N  WITH  SUPERHEAT  OF 
POUND  CONDENSING-ENG 


NSU 
IN 


team  wi 
perhea 


T^^-tfTFTHT^^^tHioiOiOiOiOiOiOtO 


•anoq  -d  -H  -j 

J9d 
urea^s  spunoj 


'd  "3.  'M 


Steam  wi 
superhea 


•anou.  'd  'H  T 

jad 
ui^a^s  spuno^ 


Steam  with 
uperheat  a 


TUBQ^S  spunoj 


•aanssaad  ppi 


COCOCOcOcOcOOl>N't^r^l>t^t^l>l>. 


i  g  s 


OOOOOOOOCOOOOOOOCX)1>I>I>1>.CO«OCO 


t>l>-QOOOOOOOOOOOOOOOOOOOOiO5O5O5 


St^CO 
O'-H 


t^t^i>i>i>i>t^t^i>i^oooooooooooo 


ooooo 


oooooooo 
iM!—  loooot^co'o 


154  SUPERHEATED  STEAM  AND  ITS  WORK 

The  superheat  of  from  400°  to  700°  F.  seems  practically  absurd,  and 
the  claim  of  less  than  10  pounds  of  steam  per  horse-power  is  only 
suited  to  an  experimental  test. 

The  saving  in  steam  by  superheat,  as  shown  in  Table  XXIV, 
say,  for  example,  at  160  pounds,  with  the  varying  mean  pressures  due 

17  42 

to  cut-off,  is,  for  200°  F.  superheat  at  £  cut-off  =  ^~^  =  1.291;  at  £ 

io.4y 

18  23  19  04 

cut-off       '..-.  =1.294;    at  ^  cut-off    j,'     =1.292,  showing  a  uniform 

increase  of  volume  of  29  per  cent,  for  various  degrees  of  cut-off  at 
200°  F.  superheat.  At  300°  F.  the  increase  in  volume  is  47  per 
cent. 

Superheating  should  not  be  regarded  as  a  means  of  carrying  more 
heat  to  an  engine,  but  only  as  a  preventive  of  waste  through  con- 
densation. It  has  been  proved  by  experiment  that  about  8°  F.  of 
superheat  are  required  to  prevent  each  1  per  cent,  of  moisture  in  the 
cylinder  at  cut-off  when  using  saturated  steam.  If  the  specific  heat 
of  superheated  steam  at  constant  pressure  be  taken  as  0.48,  it  follows 
that  a  rise  of  8°  F.  in  the  temperature  above  the  normal  temperature 
of  saturated  steam  of  the  same  pressure  represents  the  expenditure  of 
0.48x8  =  3.84  thermal  units.  Assuming  the  initial  condensation  of 
the  entering  steam  to  be  about  20  per  cent.,  then  3.84x20  =  76.8 
thermal  units  which  must  be  added  in  the  form  of  superheat  to  in- 
sure dry  steam  at  cut-off. 

The  amount  of  fuel  required  to  superheat  steam,  and  the  quantity 
of  fuel  that  must  be  burned  to  continue  this  heat,  are  greater  than  is 
commonly  supposed.  It  takes,  as  will  be  noticed  in  steam  table  XX, 
approximately  1,100  thermal  units  to  convert  a  pound  of  feed- water 
at  ordinary  temperatures  into  steam  at  the  usual  temperature.  By 
the  addition  of  76.8  thermal  units  in  the  form  of  superheat,  we  have 
increased  the  expenditure  of  heat  by  about  7  per  cent.  If  all  the  20 
per  cent,  of  condensation  is  saved  there  is  undoubtedly  a  decided 
gain ;  and  this  fact  is  true,  that  a  small  amount  of  superheat  is  desirable 
in  all  forms  of  engines.  It  is  in  the  higher  degrees  of  superheat  that 
this  difference  vanishes,  because  the  specific  heat  of  superheated  steam 
increases  with  the  degree  of  superheat. 

The  specific  heat  at  constant  pressure,  Cp,  of  superheated  steam 
at  atmospheric  pressure  and  near  the  point  of  saturation  was  found  by 


SUPERHEATED  STEAM  AND   ITS  WORK  155 

Regnault  to  be  0.48,  and  until  recently  this  value  was  thought  to  apply 
to  the  specific  heat  at  higher  pressures.  It  probably  varies,  as  does 
the  specific  heat  at  constant  volume,  Cv,  which  has  been  assigned  a 
slightly  decreasing  value  for  superheat  with  increasing  pressure,  as 
follows : 

Pressure     50  100  200  300 

Cv  0.348        0.346        0.344        0.341 

for  steam  of  moderate  superheat.  By  recent  investigations  it  has 
been  shown  that  the  specific  heat  at  constant  pressure,  Cp,  is  not 
constant,  but  that  it  is  approximately  0.65  for  100°  F.  superheat,  and 
0.75  for  200°  F.  superheat.  Using  these  values,  it  can  be  calculated 
that  the  fuel  used  to  generate  saturated  steam  with  superheat  must 
be  increased  by  the  following  percentages  in  order  to  superheat  the 
steam  to  the  various  degrees  named: 

Degree  of  superheat.  Additional  fuel  needed. 

75°  5  per  cent. 

100°  7    "      " 

150°  11    "      " 

200°  15    "      " 

Whether,  therefore,  it  is  advisable  to  superheat  the  steam  by 
direct  furnace  heat  and  increase  the  fuel-consumption  or  whether  it  is 
best  to  use  saturated  steam  is  a  problem  of  finance  rather  than  of 
engineering.  The  exception  is.  costless  superheat  by  the  waste  gases. 

Test  trials  by  Professor  Schroter,  in  Belgium,  have  shown  a  most 
decided  economy  of  superheated  steam  as  compared  with  saturated 
.steam. in  the  same  engine,  compound-condensing. 

The  total  cylinder-condensation  when  running  with  saturated 
•steam  was  9  per  cent,  of  the  total  steam  entering  the  high-pressure 
cylinder,  while  with  superheated  steam  the  cylinder-condensation  was 
but  4J  per  cent.  This  was  at  90  pounds  pressure,  with  superheat  at 
220°  F.  The  computed  economy  of  superheat  for  steam,  from  an 
average  of  many  trials,  was  12  per  cent.,  and  for  fuel  economy  an 
average  of  6  per  cent. 

Saturated  steam  on  leaving  the  boiler  carries  water  along  with  it, 
and  to  this  is  added  the  water  of  condensation  in  the  pipes  and  engine- 
•cylinder,  amounting  to  40  per  cent,  or  more  according  to  the  plant 


156  SUPERHEATED  STEAM  AND  ITS  WORK 

arrangement  and  to  the  type  of  engine.  Cylinders  provided  with 
jackets  heated  by  saturated  steam  seldom  fulfil  their  purpose,  and 
then  with  but  small  gain;  and  experience  has  shown  that  at  times 
jacketing  is  a  disadvantage.  Also,  with  saturated  steam  there  is  the 
danger  of  water-hammer  in  the  cylinder  and  valves.  This  may  be 
easily  prevented  where  superheated  steam  is  used;  for  in  this  case 
the  steam  is  kept  dry  until  a  short  time  before  leaving  the  cylinder. 
On  account  of  the  much  greater  volume  of  superheated  steam,  a 
smaller  weight  is  needed  to  fill  the  cylinder,  or,  in  other  words,  the  same 
result  is  accomplished  by  the  use  of  a  smaller  quantity  of  steam,  and 
this  in  the  case  of  a  condensing-engine  means  that  less  water  may 
be  circulated  in  the  condenser  and  consequently  smaller  pumps  may 
be  used.  Although  the  temperature  of  the  exhaust-steam  is  higher 
with  superheated  than  with  saturated  steam,  the  smaller  weight  of 
superheated  steam  more  than  compensates  for  its  high  temperature, 
and  thus  less  circulating  water  is  necessary. 

Exhaustive  comparative  tests  of  saturated  and  superheated  steam 
for  marine  purposes  have  recently  been  carried  out  on  a  steamer  called 
the  James  C.  Wallace.  This  vessel  is  one  of  the  largest  "freighters" 
on  the  lakes,  and  has  lately  been  put  into  service.  She  is  equipped 
with  two  Babcock  &  Wilcox  marine  water-tubular  boilers  with  super- 
heaters, and  the  arrangement  is  such  that  the  latter  may  be  dispensed 
with  and  saturated  steam  used.  The  engine  is  of  the  quadruple- 
expansion,  vertical  direct-acting,  jet-condensing  type.  A  comparison 
based  on  dry  coal  shows  a  net  saving  in  fuel,  with  superheated  steam, 
amounting  to  14.5  per  cent.  This  result  represents  the  combined 
increased  efficiency  of  the  machinery  plant.  The  highest  amount  of 
superheat  was  91°  F. 

While  differences  of  opinion  may  still  exist  as  to  what  type  of 
superheater  is  the  best,  the  patient  investigation  and  experiments 
that  have  been  carried  on  in  Germany  have  established  the  fact  that 
superheated  steam  can  be  used  with  locomotives  as  well  as  with 
stationary  engines.  When  the  much  greater  efficiency  of  superheated 
over  ordinary  steam  is  taken  into  consideration  there  seems  strong 
reason  to  believe  that  the  success  already  obtained  by  the  stationary 
engine  will  be  repeated  with  the  locomotive — that  materially  superior 
economy  in  power  will  be  attained  by  the  use  of  superheated  steam, 
which  will  in  time  come  into  general  use  for  locomotives. 


SUPERHEATED  STEAM  AND  ITS  WORK  157 

In  Europe  superheated  steam  is  used  with  any  type  of  engine, 
equipped  as  it  may  be  with  poppet-,  slide-,  piston-,  or  Corliss  valves; 
and  plants  built  to  use  saturated  steam  have  later  shown  the  greatest 
economy  with  superheated  steam.  Lubrication  of  the  valves  and 
cylinder  is  generally  accomplished  by  means  of  a  separate  small 
oil-pump  operated  by  the  engine  through  a  ratchet  attachment. 
With  compound  engines  a  separate  pump  is  usually  provided  for  each 
cylinder.  The  oil  used  is  a  high-grade  mineral  oil  with  a  very  high 
flashing-point,  and  is  extremely  thick.  With  turbines  a  comparatively 
smaller  pump,  operated  from  the  turbine-shaft,  is  used  to  supply  oil 
to  the  steam-inlet  and  regulating  mechanism.  A  small  pump  answers 
the  purpose,  as  a  turbine  uses  only  one-sixth  to  one-tenth  of  the  oil 
necessary  in  a  reciprocating  engine.  The  stuffing-boxes  are  made  of 
hard  metal;  bronze  or  hard  compositions  and  asbestos  or  asbestos- 
graphitic  packing  are  much  used. 

The  mechanical  difficulties  due  to  the  use  of  high-temperature 
superheat  will  no  doubt  become  a  bar  to  its  extensive  and  continued 
use.  The  disintegrating  effect  upon  the  best  lubricants  and  the  un- 
usual friction-wear  of  metal  and  packings  at  high  heat  will  eventually 
confine  the  superheat  system  to  a  limited  or  moderate  temperature 
and  to  the  more  economical  appliances  for  heat  derived  from  the 
waste  gases  of  the  chimney — instead  of  wasting  the  heat  that  should 
go  to  the  steam  in  the  boiler — by  the  use  of  fire-chamber  devices, 
or  from  the  losses  due  to  furnace  management  in  separately  fired 
superheaters. 

One  of  the  principal  wastes  in  steam-making  comes  from  the  heat 
lost  in  the  chimney,  and  any  saving  in  this  is  an  economical  gain. 
The  temperature  of  the  chimney-gases  ranges  from  250  to  400  or  more 
degrees  Fahrenheit  above  the  temperature  of  the  steam  in  the  boiler, 
and  often  much  higher  than  necessary  for  maintaining  proper  draught. 
Every  thermal  unit  rescued  from  the  chimney  and  added  to  the 
steam  in  the  cylinder  is  a  gain  that  costs  nothing  for  fuel  and  may 
add  much  to  the  economy  in  the  generation  of  steam-power,  and  may 
be  further  increased  by  the  decreased  consumption  of  fuel  under  the 
boiler. 

The  saving  due  to  the  rescue  of  heat  from  the  chimney  may  range 
from  5  to  14  per  cent,  of  the  boiler-fuel,  according  to  the  size  and 
economic  design  of  the  boiler  to  meet  its  required  work.  Often, 


158  SUPERHEATED  STEAM  AND  ITS   WORK 

boilers  that  furnish  a  scant  supply  of  steam  at  their  limit  of  pressure 
may  be  made  to  meet  the  full  requirements  by  the  simple  addition  of 
a  superheating-coil  in  the  chimney-flue. 

The  value  of  the  specific  heat  of  superheated  steam  has  been 
the  subject  of  careful  experiment,  and  by  a  formula  from  Greisman's 
experiments  the  value  for  superheat  is  given,  for  constant  pressure,  as  : 

(18)    .....    Cp  =  .00222ts-.  116,  in  which  ts 

is  the  sum  of  the  saturated  and  the  superheat  in  degrees  Fahrenheit. 
This  gives  for  100  pounds  absolute  pressure  and  100°  F.  superheat: 
327.6  +  100  =  427.6  X  .00222  =  .949  -  .116  =  .833;  and  for  the  mean  spe- 
cific heat  for  both  saturated  and  superheated  steam  at  constant 
pressure.  A  modification  of  Greisman's  formula,  viz., 

n      .833  +  .48 

Cp  =     -y-     =  .65, 

has  been  proposed,  which  is  claimed  to  be  more  nearly  correct  than 
by  using  the  accepted  formula,  viz., 


(19)  .....    .    .  C,=.  00222     *        -.116, 

which  for  100  pounds  absolute  pressure  and  100°  F.  superheat  is 
,  .  .00222 


Using  this  formula  for  the  varying  mean  specific  heat  for  different 
pressures  and  degrees  of  superheat,  the  total  heat  is  computed  by 
the  formula: 

(20)   .     .     .    .     .   1,091.7  +  .305(t  -32)  +  Cp(ts-t) 

by  which  the  following  table  (Table  XXV)  of  total  heat  has  been 
computed  for  various  temperatures  of  superheated  steam  and  abso- 
lute pressures,  using  the  varying  values  of  Cp,  as  computed  from 

formula    (19).     For   example:   for  500°  F.  Cp  =  .00222  ^50Q  +363-3\ 

-.116  =  .842,  and  1,091.7  +  .305(363.3  -  32)  +  .842(500  -  363.3)  = 
1,307.8,  or  1,308,  as  in  the  table  in  the  column  under  160  and  opposite 
500°  in  the  first  column. 


SUPERHEATED  STEAM   AND  ITS   WORK 


159 


TABLE  XXV. — TOTAL  HEAT  OF  SATURATED  AND  SUPERHEATED  STEAM  ABOVE 
32°  F.,  AT  TEMPERATURES  IN  COLUMN  1,  AND  ABSOLUTE  PRESSURES  AT  THE 
HEAD  OF  THE  OTHER  COLUMNS. 


|.a 
fc 

100 

110 

120 

130 

140 

150 

160 

170 

180 

190 

200 

380 

1,217.0 

1,214.8 

,212.6 

1,210.5 

1,208 

1,206 

1,205 

1,203 

,201 

1,199 

390 

1,224.4 

1,222.2 

,220.0 

1,218.0 

1,216 

1,214 

1,212 

1,210 

,208 

,206 

1,204 

400 

1,232.0 

1,229.8 

,227.6 

1,225.5 

,223 

1,221 

1,219 

1,217 

,215 

,214 

,212 

410 

1,239.9 

1,237.6 

,235.5 

1,233.4 

,231 

1,229 

1,227 

1,225 

,223 

,222 

,220 

420 

1,247.9 

1,245.7 

,243.5 

1,241.4 

,239 

1,237 

1,235 

1,233 

,231 

'230 

,228 

430 

1,256.3 

1,253.9 

,251.8 

1,249.7 

,247 

1,246 

1,244 

1,242 

,240 

,238 

,236 

440 

1,264.6 

1,262.4 

,260.3 

1,258.2 

,256 

1,254 

1,252 

J,  250 

,248 

1.246 

,244 

450 

1,273.3 

1,271.2 

,269.0 

1,266  0 

,265 

1,263 

1262 

,259 

,257 

1,255 

,253 

460 

1,282.3 

,280.1 

,277.9 

1,276.0 

1,273 

1,271 

,269 

,267 

,266 

1,264 

1,262 

470 

1,291.4 

,289.3 

,287.1 

1,285.0  1,283 

1,281 

,279 

,277 

,275 

1,273 

1,271 

480 

1,300.8 

,298.7 

,296.5 

1,294.0 

1,292 

1,290 

,288 

,286 

,285 

,283 

1,281 

490 

1,310.4 

,308.3 

,306.1 

1,304.0 

1,302 

1,300 

,298 

,296 

,294 

,292 

1,290 

500 

1,320.2 

,318.1 

,315.9 

1,314.0 

1,312 

1,310 

,308 

,306 

,304 

,302 

1,300 

510 

1,330.2 

,328.2 

,326.0 

1,324.0 

1,322 

1,320 

,318 

,316 

,314 

,312 

1,310 

520 

1,340.6 

,338.4 

,336.2 

1,334.0 

1,332 

1,330 

,328 

,326 

,324 

,322 

1,320 

530 

1,351.0 

,349.0 

,346.0 

1,345.0 

1,342 

1,341 

,339 

,337 

,334 

,333 

1,331 

540 

1,361.8 

,359.0 

,357.0 

1,355.0 

1,353 

1,351 

,349 

,347 

,346 

,344 

1,342 

550 

1,372.9 

,371.0 

,368.0 

1,366.0 

1,364 

1,362 

1,360 

1,358 

1,357 

,355 

1,353 

SUPERHEATERS     AND     THEIR     CONSTRUCTION 

The  most  simple  form  of  a  superheater  is  a  coil  of  ordinary  steam- 
pipe,  extra  heavy  for  wear,  bent  into  a  circular  shape  or  made  up 
with  return-bends,  and  set  in  the  chimney-flue,  or,  if  needed,  over  the 
fire  in  a  separately  fired  furnace.  The  bent  pipe-coils  are  much  in  use 
for  obtaining  high  temperatures  from  superheated  steam  in  japanning- 
ovens  and  in  vulcanizing  processes  for  hard-rubber  goods.  In  this 
manner,  by  circulating  superheated  steam  in  pipe-coils,  an  oven  tem- 
perature of  275°  may  be  readily  obtained. 

Any  form  of  superheating-coil  placed  in  the  chimney-flues  of 
boilers  having  ample  heating-surfaces  for  their  required  output  of 
steam,  and  in  which  the  economy  from  chimney-waste  has  been  kept 
within  reasonable  limits  above  the  steam  temperature,  and  from  which 
any  degree  of  superheat  can  be  obtained,  is  a  saving  without  cost. 

In  the  vast  number  of  so-called  economic  types  of  boilers  and  their 
setting,  a  saving  of  100°  F.  from  the  chimney-gases  by  superheat  in  the 
steam  will  make  a  decided  saving  in  fuel  and  in  boilers  having  large 
heat-waste  from  overwork;  a  considerable  increase  in  power  may  be 


160 


SUPERHEATED  STEAM  AND  ITS  WORK 


obtained  at  the  first  cost  of  a  simple  coil  of  pipe  and  its  setting  in  the 

chimney-flue. 

In  Fig.  126  is  shown  a  group  of  tubes  ready  for  setting  in  a  flue  or 

separate  furnace;  it  consists  of  pairs  of  cast-iron  pipes  with  solid 

bends,  arranged  as  shown,  and 
filled  with  iron-wire  coils  that 
produce  intercirculation  of  the 
steam  for  quick-heat  action  by 


FIG.  126. — Bulkley  superheater. 


convection. 

In  Fig.  127  is  shown  the 
arrangement  of  the  heater  in  a 
special  furnace — H.  W.  Bulkley 
type.  Steam  may  be  heated  to  800°  in  these  superheaters,  the  tem- 
perature of  which  is  shown  by  a  pyrometer  in  the  exit-pipe. 

In  Fig.  128  is  shown  the  Metesser  type  of  superheater-coil,  which 
consists  of  steel  tubes  bent  into  the  form  shown,  with  their  ends  ex- 
panded into  a  thick  steel  plate  with  a  steel  or  cast-iron  backing  divided 


FIG.  127. — Bulkley  superheater  in  brick  setting. 

into  two  compartments.  The  two  parts  are  bolted  together  with 
corrugated  copper  gaskets  between  the  flanges.  The  tube-section 
may  be  hung  in  a  flue-chamber  or  placed  across  the  rear  end  of  a 
water-tube  boiler,  in  which  latter  case  the  superheater  is  placed  in  and 
securely  bolted  at  the  tube-sheet  end  to  an  iron  frame,  which  is  firmly 
anchored  in  the  boiler-wall,  while  the  free  ends  of  the  tubes  enter  a 


SUPERHEATED  STEAM  AND  ITS  WORK 


161 


recess  in  the  opposite  wall  and  are  prevented  from  sagging  by  supports 
placed  between  them.  By  this  arrangement  no  joints  of  any  kind 
are  in  the  hot  gases. 

In  Fig.  129  are  represented  the  pipe-connections  for  a  return-bend 
superheater  placed  across  and  over  the  tubes  of  a  duplex  water-tube 


FIG.  128. — Metesser  superheater. 


FIG.  129. — Superheater  in  rear 
end  of  boiler. 


boiler.     Provision  is  also  made  for  flooding  the  superheater  with 
water  from  the  boiler  when  the  engine  is  not  running. 

In  Fig.   130  is  shown  a  cluster-tube  superheater  set  in  a  flue- 
chamber,  in  which  steel  tubes  of  suitable  size,  bent  into  U-shape, 
.are  flanged  on,  or  screwed  to  the  headers 
with    right-and-left    couplings   in   rows 
and  in  number  of  tubes  to  contain  the 
required  fire-surface. 

In  Fig.  131  is  shown  a  superheater 
made  with  pipe  and  return-bend  with 
rib-flanges  pushed  over  pipes  for  ex- 
tending the  heating-surface  and  for  pro- 
tection from  the  direct  contact  of  the 
gases.  It  is  placed  vertically  in  the  rear 

chamber  of  a  horizontal  tubular  boiler.      FIQ  130._Flue.chamber  super. 
This  position  of  the  superheater  does  not  heater. 


162 


SUPERHEATED  STEAM  AND  ITS  WORK 


contribute  to  the  efficiency  of  the  boiler,  although  it  may  be  an  effec- 
tive superheater.  The  principle  of  abstracting  heat  that  should  pass 
through  the  tubes  of  the  boiler  is  of  doubtful  economy. 

In  Fig.  132  is  shown  a  return-bend  coil  with  rib-flanges  placed 
in  the  rear  fire-chamber  of  a  marine  boiler.  This  form  is  also  ap- 
plicable to  the  smoke-boxes  of  locomotives,  and  in  the  various  ways 
and  designs  in  which  it  may  be  applied  adds  largely  to  counteracting 


FIG.  131. — Rear-chamber  super- 
heater. 


FIG.  132. — Superheater  at  rear 
end  of  marine  boiler. 


the  effect  of  cylinder-exposure;  as  applied  to  a  marine  boiler  the 
separate  fire,  with  its  inconvenient  conditions,  is  avoided. 

In  Fig.  133  is  shown  a  sectional  view  of  a  separately  fired  super- 
heater and  furnace.  In  the  bridge- wall  of  the  furnace  there  is  an  air- 
inlet  for  tempering  the  heat  of  the  furnace  before  it  reaches  the 
superheater-coil.  In  this  way  the  amount  of  superheat  is  controlled 
and  overheating  of  coil  prevented  when  the  engine  is  not  running. 

In  Fig.  134  are  shown  the  details  of  construction  of  the  Schwoerer 
superheater,  much  in  use  in  Europe.  The  inside  ribs  and  outside 
flanges,  cast  in  and  on  the  pipe,  with  the  method  of  connecting  them 
with  the  return-bends,  are  shown.  The  tubes  may  be  disposed  either 
vertically  or  horizontally  according  to  the  place  where  they  are  to  be 
located,  and  may  be  installed  either  in  the  uptake  from  the  boiler, 
in  the  boiler-furnace,  or  in  a  setting  to  be  separately  fired.  The 
tubes  are  of  cast  iron,  with  transverse  flanges  on  the  outside  to  take 


SUPERHEATED  STEAM  AND  ITS  WORK 


163 


up  heat  from  the  gases,  and  longitudinal  ribs  on  the  inside  to  give 
up  heat  to  the  steam.     These  flanges  and  ribs  are  necessary  on  ac- 


FIG.  133. — Superheater  with  separate  furnace. 

count  of  the  poor  conducting  power  of  the  superheated  steam,  which 
makes  it  necessary  to  have  large  surfaces  for  the  transfer  of  heat. 

This  cast-iron  construction  gives  a  large  mass  of  hot  metal  which 
serves  as  a  magazine  for  heat  and  acts  to  hold  at  an  even  tempera- 
ture the  superheated  steam  which  is  delivered.  In  making  joints  be- 
tween the  tubes  and  the  connecting-bends,  strong  flanges  are  used  con- 
nected by  heavy  bolts.  Each  flange  is  turned  with  a  circular  groove 


FIG.  134. — Schwoerer  superheater. 


FIG.  135. — Foster  superheater. 


of  triangular  section,  and  into  these  grooves  are  placed  steel  rings  of 
corresponding  form.     These  steel  rings,  strongly  compressed  between 
the  flanges,  give  an  iron-to-iron  joint  which  is  sure  to  remain  tight. 
In  Fig.  135  are  shown  some  of  the  details  of  the  Foster  superheater, 


164 


SUPERHEATED  STEAM  AND  ITS   WORK 


illustrating  the  ends  of  the  elements  connected  by  a  return-header. 
The  elements  consist  of  concentric,  seamless,  drawn-steel  tubing  pro- 
tected by  cast-iron  rings,  shrunk  on.  The  inner  tubes  are  closed  to  the 
steam,  which  is  thus  forced  through  thin  annular  spaces  and  rapidly 
superheated. 

In  Fig.  136  is  illustrated  a  longitudinal  section  of  the  Babcock  & 
Wilcox  water-tube  boiler,  with  the  location  of  the  superheater,  and  in 
Fig.  137  a  cross-section  of  the  superheater  and  its  steam-connections. 


FIG.  136. — Longitudinal  section  of  Babcock  &  Wilcox  boiler  and  superheater. 

This  superheater  is  not  subject  to  the  immediate  action  of  the 
fire,  as  the  furnace-gases  must  first  pass  through  the  front  part  of  the 
boiler,  which  comprises  a  considerable  heating-surface.  Assuming 
the  boiler  to  be  in  regular  work  and  the  firing  even,  no  great  fluctua- 
tions in  temperature  can  take  place  where  the  superheater  is  fixed. 
Moreover,  it  is  readily  accessible  for  examination  and  for  the  renewal 
of  tubes. 

There  are  no  flanged  joints;  all  the  tube-joints  are  expanded  and 
freedom  for  expansion  is  provided  by  the  tubes  being  free  at  one  end, 
and  by  the  manifolds  not  being  rigidly  connected  with  each  other. 


SUPERHEATED   STEAM  AND  ITS  WORK 


165 


FIG.  137. — Cross-section  Babcock  &  Wil- 
cox  superheater. 


Prevention  against  overheating  during  steam-raising  is  insured 
by  the  arrangement  for  flooding  with  boiler-water  and  using  the  super- 
heater as  part  of  the  boiler  heating-surface  while  steam  is  being  raised 
or  when  it  is  desired  to  use  satu- 
rated steam. 

As  will  be  seen,  the  tubes  are 
bent  into  a  U-shape  and  con- 
nected at  both  ends  with  mani- 
folds, one  of  which  receives  the 
natural  steam  from  the  boiler,  the 
other  collecting  the  superheated 
steam  after  it  has  traversed  the 
superheater-tubes  and  delivering 
it  to  the  valve  placed  above  the 
boiler. 

The  flooding  arrangement  con- 
sists merely  of  a  connection  with 
the  water-space  of  the  boiler-drum 
and  a  three-way  cock,  by  which  the  water  enters  the  lower  manifold 
and  fills  the  superheater  to  the  boiler  water-level.  Any  steam  formed 
in  the  superheater-tubes  is  returned  to  the  boiler-drum  through  the 
collecting-pipe,  which,  when  the  superheater  is  at  work,  conveys 
saturated  steam  into  the  upper  manifold  through  the  heating-tubes, 
and  from  the  lower  manifold,  by  two  tubes  outside  of  the  drum,  to 
the  fitting  at  the  top  of  the  boiler. 

In  Fig.  138  is  shown  a  section  of  the  W.  Schmidt  superheater. 

The  management  of  superheaters  is  of  interest,  and  we  append  a 
short  description  of  the  Schmidt  superheater,  which  is  also  applicable 
to  other  types  or  models. 

Superheating  steam  under  the  Schmidt  system  may  be  effected 
in  one  of  two  ways,  either  by  placing  the  superheater  in  a  chamber 
between  the  boilers  and  the  main  flue — this  being  known  as  the  flue-' 
fired  superheater — and  using  a  portion  of  the  hot  gases  direct  from 
the  boiler-flue,  or  by  having  an  independent,  direct-fired  superheater 
through  which  the  saturated  steam  from  the  boiler,  or  battery  of 
boilers,  is  made  to  pass  before  reaching  the  engine.  The  illustration 
(Fig.  138)  represents  a  section  of  the  setting  and  the  construction 
of  the  apparatus. 


166 


SUPERHEATED   STEAM  AND   ITS  WORK 


The  saturated  steam  enters  through  the  valve  at  the  top,  and, 
having  been  dried  in  the  upper  half  of  the  apparatus,  is  led  through 
suitable  passages  to  the  bottom  tubes,  cooling  them  from  the  inside 
and  so  protecting  them  from  deterioration.  It  then  flows  in  the  same 
direction  as  the  flue-gases,  taking  up  heat  from  them  on  the  way. 
The  higher  the  temperature  of  the  steam,  the  less  that  of  the  gases, 
and  the  steam  leaves  the  superheater  when  it  is  hottest.  The  gases 

leave  the  superheating- 
coils  at  about  900°  F., 
and  pass  on  to  the  drying- 
coils,  whence  they  enter 
the  main  flue  at  a  tem- 
perature of  about  460°  F. 
The  heat  of  the  gases  is 
thus  utilized  to  the  high- 
est possible  extent,  while 
at  the  same  time  the  tubes 
are  sufficiently  protected 
from  excessive  heat. 

The  superheater  con- 
sists of  a  number  of  coils 
of  equal  size  and  dimen- 
sions, the  ends  of  which 
are  fixed  to  cast-iron 
junction-boxes.  All  boxes 
are  placed  outside  the 
chamber,  thus  avoiding 
contact  with  the  flue- 


FIG.  138. — Schmidt  superheater. 


gases,  and  are  easily  accessible  even  when  the  superheater  is  in  service. 
Each  coil  can  be  taken  out  separately  and  a  new  one  put  in  without 
removing  the  others  or  dismantling  the  plant.  If  one  coil  becomes 
defective,  it  need  not  be  replaced  at  once;  the  ends  can  be  stopped 
with  blank  flanges  in  a  few  minutes,  and  the  tube  replaced  when 
convenient. 

All  the  water  produced  by  condensation  while  the  superheater  is  idle 
collects  in  the  bottom  junction-box  and  escapes  through  the  drain-cock. 

The  outside  of  the  coils  should  be  cleaned  at  intervals  according 
to  the  nature  of  the  fuel  employed.  The  cleaning  is  effected  with  a 


SUPERHEATED  STEAM  AND   ITS  WORK  167 

jet  of  steam  in  the  usual  way.  A  steel  mercury  thermometer,  scaled 
to  900°  F.,  is  fitted  where  the  superheated  steam  enters  the  main 
steam-pipe,  and  has  a  red  mark  to  indicate  the  maximum  tempera- 
ture. When  this  mark  is  passed,  an  electric  bell  rings  as  long  as  the 
maximum  temperature  is  exceeded.  A  thermometer-pocket  is  also 
provided,  in  which  a  glass  thermometer  can  be  placed  for  checking 
the  steel  mercury  thermometer. 

When  starting,  the  superheater  should  be  warmed  with  steam 
while  the  engine  is  warming  up,  and  care  should  be  taken  to  leave 
the  drain-cock  open  until  the  engine  has  actually  started.  After  the 
engine  has  run  for  a  few  minutes  the  cock  should  be  closed  and  the 
superheater  brought  into  operation. 

If  by  chance  the  steam  should  be  Suddenly  cut  off,  the  air-door 
underneath  the  lowest  junction-box  should  be  opened  to  enable  cool 
air  to  enter  and  protect  the  tubes  from  the  fire  and  from  radiation  of 
heat  from  the  walls.  This  door  is  automatically  worked  by  a  valve 
kept  closed  by  a  weight  attached  to  an  outside  lever.  A  chain  con- 
nects the  weight  with  the  air-door  and  tends  to  keep  it  open.  As 
soon  as  the  steam  begins  to  flow  it  presses  the  valve  downward,  and 
as  the  valve  falls  the  weight  is  lifted  and  closes  the  door. 

Where  an  engine  works  continuously,  and  is  in  charge  of  a  com- 
petent stoker,  this  apparatus  is  unnecessary,  and  can  be  put  out  of 
action  by  merely  disconnecting  the  chain,  but  in  cases  of  irregular 
working,  and  especially  when  the  engine  is  liable  to  be  stopped  sud- 
denly without  the  stoker's  knowledge,  the  arrangement  is  of  the 
greatest  importance. 

As  a  general  rule  the  stoking  of  the  superheater  should  cease 
about  three-quarters  of  an  hour  before  the  engine  is  to  be  stopped,  so 
that  when  the  superheater  is  put  out  of  action  the  fire  will  be  out 
and  the  bricks  cooled  down  to  some  extent.  During  this  period  the 
temperature  gradually  decreases,  but  the  stored  heat  is  sufficient  to 
keep  the  steam  at  the  required  temperature  until  the  engine  stops. 

This  apparatus  is  manufactured  by  the  Providence  Engineering 
Works. 

The  conditions  for  enabling  the  use  of  high-pressure  steam  and 
high  superheat  with  safety  may  be  summarized  as  follows: 
1.  A  large  factor  of  safety. 


168 


SUPERHEATED  STEAM  AND  ITS  WORK 


2.  Steam  and  water  capacity  sufficient  to  care  for  sudden  fluctua- 
tions of  load. 

3.  A  proper  arrangement  of  heating-surface  to  thoroughly  absorb 
the  heat  of  the  gases. 

4.  The  absence  of  any  stayed  surfaces. 

5.  Straight  tubes,  so  that  they  can  be  cleaned  easily,  and  so  that 
one  can  see  through  them  and  know  that  they  are  clean. 

6.  Sectional  construction  to  insure  safety  and  ease  of  repair. 

7.  Wrought-steel  construction  throughout. 

8.  Ample  surface  to  disengage  the  steam  easily  so  as  to  avoid 
priming  or  a  fluctuating  water-level. 

9.  Expansion  and  contraction  properly  provided  for. 

10.  And  last,  but  not  least,  a  perfect  and  positive  circulation  of 
the  water  in  the  boiler. 

Added  to  the  above  it  is  imperative,  on  the  score  of  economy,  that 
the  soot  can  be  easily  removed  from  the  heating-surface  while  the 
boiler  is  in  operation,  preferably  by  means  of  air-  or  steam-jets. 

In  Fig.  139  is  illustrated  a  high-pressure  boiler  of  the  Babcock 
&  Wilcox  type  with  a  double  bend  superheater  coil  set  in  the  upper 


FIG.  139. — Boiler  and  superheater  for  200  pounds  pressure  and  150°  F.  superheat. 

Babcock  &  Wilcox  type. 


SUPERHEATED  STEAM  AND  ITS   WORK 


169 


chamber  with  its  connections  to  the  boiler  shell,  arranged  as  before 
described. 

In  conclusion,  it  might  be  well  to  further  emphasize  the  advantages 
of  moderate  superheat  of,  say,  100  to  150°  F. 

In  most  plants,  if  properly  piped  and  protected,  this  amount  of 
superheat  will  not  only  avoid  condensation  in  the  steam-mains,  but 
will  practically  eliminate  the  condensation  losses  in  the  high-pressure 
cylinders  of  the  engine,  and  this  alone  will  show  an  actual  saving, 
varying  from  10  to  25  per  cent,  according  to  the  class  of  engine  and 
its  condition.  This,  coupled  to  the  saving  effected  by  the  use  of  high- 
pressure  steam,  and  to  boilers  that  can  be  cleaned  and  kept  up  to  their 
efficiency  while  at  work,  is  of  such  importance  in  considering  the 
cost  of  operation  that  no  thinking  user  of  steam  can  afford  to  dis- 
regard it. 


THE     MEASUREMENT    OF    STEAM-CONSUMPTION 

The  quantity  and  value  of  steam  sold  for  heating  and  power 
purposes   to  other  parties,  and  which  must  be  delivered  through 


FIG.  140. — Steam-meter. 


FIG.  141. — Section  of  the  steam-meter. 


pipes,  may  be  measured  with  fair  accuracy,  even  when  its  use  is  varia- 
ble or  intermittent. 

In  Figs.  140  and  141  we  illustrate  the  automatic  recording  steam- 
meter  of  Mr.  G.  C.  St.  John,  of  New  York  City,  which  makes  a  record 
on  a  chart  moved  by  clock-work  that  shows  the  horse-power  that  is 


170  SUPERHEATED  STEAM   AND   ITS   WORK 

being  used  at  all  times,  and  the  aggregate  per  day  or  month.  Many 
hundreds  are  in  use  in  the  New  York  steam  service  and  throughout  the 
country.  The  lifting  of  a  conical  valve  by  differential  pressure  allows 
the  required  quantity  of  steam  to  pass  through  the  annular  area,  which 
is  the  measure  under  the  initial  pressure.  The  valve-lift  is  recorded 
on  a  strip  of  paper  moved  by  a  clock;  the  mean  of  the  record-curves 
being  the  measure  for  the  time.  The  marking-hand  is  moved  by  a 
lever  from  the  conical  valve  and  by  a  small  transfer-shaft  through  the 
projecting  hollow  arm  from  the  cylinder.  The  small  chamber  at  the 
bottom  is  a  dash-pot  filled  with  water,  which  keeps  the  valve  from 
chattering. 

The  sale  of  steam  for  power  and  for  heating  purposes,  in  manu- 
facturing districts,  is  generally  made  in  horse-power  units,  and  when 
supplied  to  engines  only,  the  indicated  horse-power  of  the  engine  is 
the  usual  measure  of  the  steam-supply,  unless  the  waste  by  condensa- 
tion in  long  pipe-lines  may  require  an  additional  allowance. 

For  heating  purposes  the  unit  for  the  price  may  be  the  same  as 
for  power;  but  the  method  used  for  obtaining  the  unit,  when  meter 
measurement  is  out  of  the  question,  is  often  a  matter  of  controversy 
from  personal  differences  in  regard  to  space,  and  exposure  of  heated 
areas  and  their  required  temperature.  The  only  reliable  method 
of  measurement  that  is  available  is  derived  from  the  weight  of  water 
drained  from  the  heating-pipes  and  its  weight  as  steam  at  the  pressure 
in  the  supply-pipe. 

The  horse-power  in  ordinary  slide-valve  engines  varies  somewhat 
from  20  pounds  per  horse-power  hour,  which  may  be  taken  as  a  fair 
average  for  indicating  the  amount  of  steam  used  for  heating  purposes. 


CHAPTER    XII 

ADIABATIC   EXPANSION   OF   STEAM 

IN  adiabatic  expansion  without  loss  or  gain  in  heat  from  outside 
source  or  from  the  walls  of  a  cylinder,  the  terms  of  expansion  are: 


;  then    ?=        and       =  ;  also, 

±1        V2y  V2        \"l/ 

(y  \  y-1       /p  \y-l 
^M      =  I  p-1  y  j  and  is  also  applicable  to  the  relation  of  pressures 


and  volumes  to  temperatures,  and 

1     T2  . 


sure  in  pounds  absolute  or  per  square  foot,  V  =  volumes  in  cubic  feet, 
r  =  ratio  of  volumes.     T  =  temperatures  before  and  after  expansion. 

The  ratio  exponent  in  any  equation  for  the  adiabatic  expansion 
of  steam  is  variable  as  discussed  by  leading  authorities,  and  as  a 
sensibly  perfect  gas  or  superheated  steam  is  given  as  1.35;  and 
for  saturated  steam  varying  from  1.3  to  1.111,  by  different  authors, 
or  ^-,  as  adopted  by  Rankine  for  the  consideration  of  the  actual 
condition  of  steam  behind  a  moving  piston.  Probably  there  is  no 
exact  empirical  value  for  y  for  the  varying  influences  in  the  make-up 
and  time  of  expansion  in  a  steam-cylinder.  Professor  Wood  gives 
the  specific  heat  of  steam  at  constant  pressure,  Cp  =  373.44,  and  for 


AA 

constant  volume,  Cv  =  290.16,  and     £  =  <        -~  =  1.2869  =  y  for  their 


ratio  in  foot-pound  values. 

Professor  Zeuner  found  that  the  value  of  y  depended  upon  the 
specific  volume  of  the  steam  for  the  same  initial  condition  at  from 
1  to  4  atmospheres,  and  that  the  true  value  may  be  represented 
by  the  empirical  formula: 

(21)  .  .  y  =  1  .035  +  0.  lOOx,  x  being  derived  from  the  formula  used  for 
computing  Column  8,  Table  XXI,  which  is  proportional  for  the  expan- 
sion of  steam  from  160  absolute  to  other  lower  pressures. 

171 


172 


ADIABATIC  EXPANSION  OF  STEAM 


Then  for  any  degree  of  expansion  between  limited  pressures  the 
exponent  y  will  be  1.035+0.100x,  as  computed  by  formula  (21). 
For  expansion  from  160  to  15  pounds  absolute  x  may  be  taken 

as  .865  X  0.100  =  .0865  +  1.035  =  1.1215  =  y,  and  i  =  .891.     Then 

y 

(PA!     IfiO 
^\y  =  ^  =  10.66   log.  1.027787 X. 891  =0.915758217  =  index  8.237, 
-T2/  15 

the  volume  of  saturated   steam  expanded  from  160  to  15  pounds 
absolute. 

The  water  of  condensation  by  the  expansion  of  steam  in  this  ex- 

TABLE  XXVI. — REAL  CUT-OFF,  CORRESPONDING  TO  THE  APPARENT  CUT-OFF,  FOR 
DIFFERENT  FRACTIONS  OF  CLEARANCE. 


fi- 

Real cut-off  for  fraction  of  clearance  of 

ll 

.01 

.02 

.03 

.04 

.05 

.06 

.07 

.08 

.09 

.08 

.090 

.098 

.106 

.115 

.124 

.132 

.140 

.148 

.155 

.10 

.109 

.118 

.126 

.135 

.143 

.151 

.159 

.167 

.174 

.12 

.129 

.138 

.146 

.154 

.162 

.170 

.177 

.185 

.192 

.14 

.149 

.158 

.165 

.174 

.181 

.189 

.196 

.204 

.211 

.16 

.169 

.177 

.184 

.193 

.200 

.207 

.215 

.222 

.229 

.18 

.189 

.197 

.204 

.212 

.219 

226 

.233 

.240 

.247 

.20 

.208 

.216 

.223 

.231 

.238 

.245 

.252 

.259 

.266 

.22 

.228 

.236 

.243 

.251 

.257 

.264 

.271 

.277 

.284 

.24 

.248 

.256 

.262 

.270 

.276 

.283 

.290 

.296 

.303 

.26 

.268 

.275 

.281 

.289 

.295 

.302 

.308 

.315 

.321 

.28 

.288 

.295 

.301 

.308 

.314 

321 

.327 

.333 

.339 

.30 

.307 

.314 

.320 

.327 

.333 

340 

.346 

.352 

.358 

.32 

.327 

.334 

.340 

.346 

.352 

.359 

.364 

.370 

.376 

.34 

.347 

.354 

.359 

.366 

.371 

.378 

.383 

.389 

.395 

.36 

.367 

.373 

.378 

.385 

.390 

.396 

.402 

.407 

.413 

.38 

.387 

.393 

.398 

.404 

.409 

.415 

.420 

.425 

.431 

.40 

.406 

.412 

.417 

.423 

.429 

.434 

.439 

.444 

.450 

.42 

.426 

.432 

.437 

.442 

.448 

.453 

.458 

.462 

.468 

.44 

.446 

.452 

.456 

.462 

.467 

.472 

.477 

.481 

.486 

.46 

.465 

.471 

.475 

.481 

.486 

.490 

.495 

.500 

.504 

.48 

.485 

.491 

.495 

.500 

.505 

.509 

.514 

.518 

.522 

.50 

.505 

.510 

.514 

.519 

.524 

.528 

.533 

.537 

.541 

.52 

.525 

.530 

.534 

.538 

.543 

.547 

.551 

.555 

.559 

.54 

.545 

.550 

.554 

.558 

.562 

.566 

.570 

.574 

.578 

.56 

.564 

.569 

.573 

.577 

.581 

.585 

.589 

.593 

.596 

.58 

.584 

.589 

.593 

.596 

.600 

.604 

.607 

.611 

.614 

.60 

.604 

.608 

.612 

.615 

.619 

.623 

.626 

.630 

.633 

.62 

.624 

.628 

.632 

.634 

.638 

.642 

.645 

.648 

.651 

ADIABATIC  EXPANSION  OF  STEAM  173 

ample  is:  1  —  .865,  or  13J  per  cent.  ;  and  from  the  ratio  of  volumes  at  the 

25  85  8  237 

above  pressures      '     =  9.232,  and   '=.  Ill  per  cent,  condensation 


from  the  effect  of  expansion  alone. 

In  practice,  the  cooling  effect  of  the  cylinder-walls  increases  the 
percentage  of  condensation,  which  may  reach  25  per  cent,  in  slow- 
running  engines.  Thus  the  speed  of  piston  is  one  of  the  claims  for 
economy  for  high-speed  engines. 

The  values  of  the  real  cut-off  in  the  table  are  derived  from  the 

equation  -  —  >  in  which  r  =  the  ratio  of  the  apparent  cut-off,  and  c  = 
the  percentage  of  clearance.  For  example:  for  .30  cut-off  with  7  per 
cent,  clearance,  .30  +  .07  =  .37,  and  -^-  =  .3457,  or  .346,  as  in  the  table. 

The  formulas  for  mean  forward  pressure  of  expanding  steam,  as 
given  by  authorities  who  have  critically  investigated  this  subject, 
vary  somewhat  from  the  results  given  by  the  hyperbolic  formula, 
which  is  now  accepted  as  more  nearly  meeting  the  exact  conditions 

of  steam-engine  practice.     Rankine's  formula  PI  I-  ---  —  )  seems  to 


give  for  mean  forward  pressure  about  2  per  cent,  in  excess  of  the 
hyperbolic  formula. 

In  Table  XXVII  are  given  the  decimal  multipliers  for  the  mean 
forward  absolute  pressure,  with  the  apparent  or  nominal  cut-off  and 
clearance  of  from  1  to  10  per  cent,  of  the  stroke  of  the  piston. 

For  obtaining  the  multiplier  for  mean  forward  pressure  for  any 
absolute  pressure,  as  shown  in  the  table,  from  the  hyperbolic  formula, 
we  have 

(22)     .     .     (-  hhyR ]°g'  R X  1  +  c\  - c,  in  which  R  =  the  ratio  of  ex- 
pansion, or  —  — ,  as  in  Table  XXVI.     Then  by  substituting  the 
real  cut-off 

values  for,  say,  .30  cut-off  and  7  per  cent,  clearance,  we  have 

37  1 

-  =  .346  and  — —  =  2.89,  the  ratio  R  of  expansion,  the  hyp.  log. 
1.07  .o4o 

2  Q613 
of  which  is  1.0613  +  1=^^  =  .713X1.07  =  .762 -.07  =  .692,  as  in 

the  table. 


174 


ADIABATIC  EXPANSION  OF  STEAM 


TABLE   XXVII. — MEAN  FORWARD  PRESSURE  FROM  ABSOLUTE  INITIAL  PRESSURE, 
WITH  ACTUAL  CLEARANCE  DUE  TO  THE  NOMINAL  CUT-OFF. 


<§! 

Clearance,  per  cent,  of  stroke. 

=  1 

.01 

.02 

.03 

.04 

.05 

.06 

.07 

.08 

.09 

10 

iV 

.10 

.344 

.357 

.369 

.381 

.392 

.402 

.413 

.423 

.432 

.441 

.111 

.368 

.380 

.391 

.402 

.413 

.423 

.433 

.442 

.451 

.459 

£ 

.125 

.397 

.403 

.418 

.429 

.439 

.448 

.457 

.467 

.474 

.482 

^. 

.143 

.432 

.442 

.452 

.460 

.470 

.479 

.488 

.495 

.503 

.510 

i 

.167 

.475 

.484 

.493 

.501 

.509 

.517 

.524 

.531 

.538 

.545 

1 

.20 

.530 

.538 

.545 

.552 

.559 

.566 

.572 

.578 

.584 

.590 

.25 

.603 

.609 

.615 

.621 

.626 

.631 

.637 

.641 

.646 

.650 

3 

.30 

.666 

.671 

.675 

.679 

.685 

.688 

.692 

.697 

.701 

.705 

.333 

.704 

.708 

.712 

.716 

.719 

.722 

.726 

.731 

.734 

.737 

.40 

.769 

.772 

.776 

.778 

.781 

.784 

.787 

.789 

.791 

.794 

.50 

.848 

.850 

.852 

.854 

.856 

.858 

.860 

.861 

.863 

.864 

.625 

.919 

.920 

.921 

.923 

.925 

.925 

.926 

.927 

.927 

.928 

.75 

.967 

.967 

.968 

.968 

.969 

.969 

.969 

.970 

.970 

.970 

From  the  mean  absolute  forward  pressure  the  actual  back  pressure 
must  be  subtracted  for  obtaining  the  mean  effective  pressure  due  to 
the  piston-stroke.  If  the  exhaust  is  directly  to  the  atmosphere,  the 
atmospheric  pressure,  plus  the  back  pressure  due  to  the  friction  in 
pushing  the  steam  before  the  piston  and  through  the  exhaust-pipe, 
will  be  the  total  back  pressure. 

The  variation  of  the  atmospheric  pressure  may  be  from  14  to  15 
pounds,  according  to  the  barometric  pressure,  and  the  back  pressure 
from  1  to  3  pounds  more,  depending  upon  the  frictional  conditions 
in  the  exhaust. 

Terminal  pressure  is  due  to  the  stroke  as  1  divided  by  the  ratio  of 
expansion,  or  1  divided  by  the  real  cut-off,  as  found  in  Table  XXVI, 
which  gives  the  ratio  of  expansion;  and  for  the  last  example 


=  2.89,  and 


-346,  the  multiplier  for  the  initial  absolute 


pressure. 

For  example:  for  100  pounds  initial  absolute  pressure,  T^  cut- 
off with  7  per  cent,  clearance  the  mean  forward  pressure  per  Table 
XXVII  is  .692;  the  real  cut-off  per  Table  XXVI  is  .346,  which  is 
also  the  ratio  for  the  terminal  absolute  pressure  in  Table  XXVIII. 

Then,  for  example,  100  X.  692  x.  346  =  23.94,  absolute,  and  23.94- 
14.7  =  9.2,  the  terminal  gauge  pressure.  . 


ADIABATIC  EXPANSION  OF  STEAM 


175 


TABLE  XXVIII. — TERMINAL  ABSOLUTE  PRESSURE  DUE  TO  THE  ABSOLUTE  FORWARD 
PRESSURES  AND  CLEARANCE,  AS  GIVEN  IN  TABLE  XXVII.  ABSOLUTE  INITIAL 
PRESSURE  X  MEAN  FORWARD  PRESSURE  X  TERMINAL  PRESSURE  DUE  TO  CUT- 
OFF =  TERMINAL  ABSOLUTE  PRESSURE. 

ta-  Terminal  absolute  pressure  for  fraction  of  clearance  of 


I 

8 

: 

.01 

.02 

.03 

.04 

.05 

.06 

.07 

.08 

.09 

.08 

.09 

.098 

.106 

.115 

.124 

.132 

V  .140 

.148 

.155 

.10 

.109 

.118 

.126 

.135 

.143 

.151 

.159 

.167 

.174 

.12 

.129 

.138 

.146 

.154 

.162 

.170 

.177 

.185 

.192 

.14 

.149 

.158 

.165 

.174 

.181 

.189 

.196 

.204 

.211 

.16 

.169 

.177 

.184 

.193 

.200 

.207 

.215 

.222 

.229 

.18 

.189 

.197 

.204 

.212 

.219 

.226 

.233 

.240 

.247 

.20 

.208 

.216 

.223 

.231 

.238 

.245 

.252 

.259 

.266 

.22 

.228 

.236 

.243 

.251 

.257 

.264 

.271 

.277 

.284 

.24 

.248 

.256 

.262 

.270 

.276 

.283 

.290 

.296 

.303 

.26 

.268 

.275 

.281 

.289 

.295 

.302 

.308 

.315 

.321 

.28 

.288 

.295 

.301 

.308 

.314 

.321 

.327 

.333 

.339 

.30 

.307 

.314 

.320 

.327 

.333 

.340 

.346 

.352 

.358 

.32 

.327 

.334 

.340 

.346 

.352 

.359 

.364 

.370 

.376 

.34 

.347 

.354 

.359 

.366 

.371 

.378 

.383 

.389 

.395 

.36 

.367 

.373 

.378 

.385 

.390 

.396 

.402 

.407 

.413 

.38 

.387 

.393 

.398 

.402 

.409 

.415 

.420 

..425 

.431 

.40 

.406 

.412 

.417 

.423 

.429 

.434 

.439 

.444 

.450 

.42 

.426 

.432 

.437 

.442 

.448 

.453 

.458 

.462 

.468 

.44 

.446 

.452 

.456 

.462 

.467 

.472 

.477 

.481 

.486 

.46 

.465 

.471 

.475 

.481 

.486 

.490 

.495 

.500 

.504 

.48 

.485 

.491 

.495 

.500 

.505 

.509 

.514 

.518 

.522 

.50 

.505 

.510 

.514 

.519 

.524 

.528 

.533 

.537 

.541 

The  available  heat  in  steam  for  power  is  essentially  the  sensible 
heat,  that  can  create  energy  by  expansion  from  any  initial  temperature 
and  pressure  to  some  lower  temperature  and  pressure.  The  total 
available  energy  from  85  pounds  gauge,  100  absolute,  is:  327.6-212 
=  115.6°  F.X  778  =  89,936  foot-pounds,  or  nearly  2}  horse-power  per 
pound  of  steam — less  friction,  condensation,  radiation,  and  leakage— 
in  any  mechanical  device  for  utilizing  its  energy. 

The  available  heat  of  the  exhaust  (latent  heat)  is  between  its 
temperature  at  atmospheric  pressure  and  the  temperature  of  the 
water  after  condensation,  say  150°  F.;  then  212  - 150  =  62°  X  778  = 
48,226  foot-pounds,  or  nearly  1J  horse-power  per  pound  of  steam. 
Then  4J  horse-power  is  the  greatest  available  energy  that  can  be 
obtained  from  1  pound  of  steam,  at  85  pounds  gauge-pressure,  by 
expansion  and  condensation.  The  practical  operation  of  conversion 
is  variable,  and  much  less  than  the  theoretical  deduction. 


176  ADIABATIC  EXPANSION  OF  STEAM 

Steam,  when  suddenly  expanded,  as  in  a  cylinder,  suffers  condensa- 
tion by  a  small  percentage,  and  the  latent  heat  thus  liberated  is  added 
to  the  remaining  uncondensed  steam.  The  amount,  independent  of 
the  condensation  by  contact  with  the  cylinder-walls,  is  shown  in 
Column  x,  Table  XXI,  and  by  the  formula  from  which  that  column 
was  computed. 

When  steam  is  compressed,  as  in  cylinder-compression,  the  contrary 
effect  is  produced;  the  heat  generated  by  compression  is  added  to  the 
steam  and  it  becomes  superheated.  The  economy  of  high-pressure 
steam  has  become  more  evident  as  discussion  and  experimentation 
have  greatly  advanced  its  possibilities  during  the  past  two  decades; 
so  that  practically,  from  theoretical  deduction,  the  total  heat  that  is 
available  for  power  advances  with  the  initial  pressure  at  a  greater 
rate  than  the  latent  heat,  as  shown  in  the  total  latent-heat  col- 
umns of  the  table  of  properties  of  saturated  steam  (Table  XX).  For 
instance,  the  difference  at  100  pounds  absolute  is  298.9  heat-units, 
and  at  200  pounds  is  355  heat-units,  or  over  18  per  cent,  in  available 
heat-units. 

The  interchangeable  heat  effect  from  steam  in  contact  with  the 
surface  of  the  cylinder-walls  is  made  evident  by  the  well-known 
difference  in  temperature  of  the  steam  at  entrance  and  at  exhaust. 
From  the  initial  temperature  during  the  period  of  admission,  every 
part  of  the  cylinder-walls  in  con  tact  with  the  incoming  steam — cylinder- 
head,  piston,  piston-rod,  and  passages — receives  heat  from  the  initial 
temperature  of  the  steam;  during  which  time  condensation  takes 
place  upon  their  surface,  and  the  latent  heat  liberated  by  condensation 
is  absorbed  by  the  cylinder-walls,  which  have  become  cooled  by  the 
lower  temperature  of  the  previous  exhaust.  During  the  period  of 
expansion  the  temperature  of  the  steam  falls,  so  that  at  near  the 
terminal  it  is  below  that  of  the  walls  that  received  heat  by  the  previous 
admission,  and  reevaporation  takes  place;  thus  latent  heat  is  liberated 
by  transfer  during  admission  and  absorbed  by  reevaporation  during 
expansion  and  the  exhaust.  The  balance  is  small  with  high-speed 
pistons,  yet  in  no  case  is  there  an  absolute  balance  obtained,  except 
at  the  expense  of  steam-jacket  addition  of  heat  to  counteract  radiation 
and  air-convection. 


ADIABATIC   EXPANSION  OF  STEAM  177 


ECONOMY      OF      THE      SIMPLE      HIGH-SPEED 
ENGINE 

During  the  past  two  decades  the  economy  of  steam-engine  design 
and  its  use  of  steam  has  been  a  fruitful  source  of  discussion  and  ex- 
periment, resulting  in  reducing  the  comparative  length  of  stroke,  in 
increase  of  speed,  and  in  the  adoption  of  more  perfect  and  automatic 
valve-motion  and  economic  cut-off.  These  points  are  still  variable 
in  the  designs  of  engine-builders,  but  are  verging  toward  a  uniform 
ideal.  Both  theory  and  practice  now  show  that  increased  economy 
in  the  use  of  steam  is  found  from  increased  pressure  to  certain  limits 
for  single-expansion,  from  the  fact  that  there  is  more  heat  in  higher- 
pressure  steam  available  for  doing  work,  in  proportion  to  the  amount 
of  heat  required  to  generate  the  steam,  than  in  the  case  of  low-pressure 
steam  with  its  proportionate  loss  in  doing  useless  work;  nor  is  there 
any  gain  in  extremety  high  pressure  for  single-cylinder  engines,  because 
of  the  loss  from  condensation  due  to  the  extreme  range  of  temper- 
ature that  would  result  from  extreme  pressures. 

In  a  simple  non-condensing,  high-speed  engine  the  limit  of  economic 
pressure  may  be  at  115  pounds  gauge-pressure,  and  in  simple  con- 
densing-engines  there  is  little  advantage  with  steam  above  90  pounds. 

In  the  long-stroke  system,  with  single  valves  and  long  steam- 
passages,  it  is  certain  there  is  a  large  amount  of  cooling-surface  that 
the  steam  is  in  contact  with,  while  entering  the  cylinder,  that  is  cooled 
by  the  lower  temperature  of  the  exhaust  through  the  same  passages. 

When  the  valves  are  close  to  the  ends  of  the  cylinder,  as  in  Corliss 
and  other  types  of  four-valve  engines,  the  surfaces  of  the  ports  and 
port-passages  are  reduced  to  only  a  trifle  greater  than  due  to  the  thick- 
ness of  the  cylinder- wall,  which  leaves  only  the  cylinder-heads  and 
piston  with  the  small  section  of  cylinder-wall  to  condense  the  incoming 
steam.  In  this  type  of  engine  there  is  economy. 

In  the  single-valve  automatic  engine  we  have  a  condition  that, 
while  simple  and  compact,  loses  a  little  in  economy,  because  of  the 
long  steam-passages,  and  from  the  fact  that  the  cool  exhaust-steam 
must  pass  through  the  same  passages  and  the  same  valve  from  which 
the  live  steam  enters.  With  engines  having  the  single  valve  there  is 


178  ADIABATIC  EXPANSION  OF  STEAM 

not  as  good  steam-distribution  as  when  two  or  four  valves  are  used, 
with  double  eccentrics.  In  the  single-valve  engines  the  characteristics 
are  that  the  earlier  in  the  stroke  the  steam  is  cut  off,  the  greater  will 
be  the  compression,  and  that  at  very  early  cut-off  the  compression  will 
become  excessive;  thus  we  see  that  it  is  not  possible  to  operate  the 
engine  with  an  early  cut-off  and  realize  the  full  benefit  of  expansion. 
The  clearance-surfaces  are,  however,  warmed  up  by  the  compression, 
which  is  a  benefit  in  its  way. 

There  is  no  definite  rule  which  would  tell  how  far  to  carry  the 
expansion  in  any  particular  case,  although  it  is  generally  considered 
that  the  best  results  are  obtained  in  the  case  of  non-condensing  engines 
when  cutting  off  at  about  one-third  stroke.  With  a  simple  condensing- 
engine  the  best  results  are  usually  obtained  when  cutting  off  at  from 
one-sixth  to  one-fourth  stroke.  In  compound  engines  varying  de- 
grees of  expansion  are  used,  the  point  of  cut-off  in  the  high-pressure 
cylinder  usually  being  adjusted  to  give  from  12  to  20  expansions  in 
both  cylinders. 

When  an  engine  is  overloaded  it  is  useless  to  expect  to  operate 
with  economy,  and  the  same  will  apply  when  the  engine  is  too  large 
to  do  the  work,  because  the  point  of  cut-off  will  come  in  one  case  too 
late,  and  in  the  other  too  early,  for  the  economical  use  of  steam.  If 
the  cut-off  occurs  too  early  there  will  be  an  increased  loss  from  cylinder- 
condensation,  and  if  too  late,  the  expansion  of  the  steam  will  not  be 
carried  out  as  far  as  it  should  be.  It  has  been  found  that  when  an 
engine  is  running  under  these  conditions  it  is  better,  if  possible,  to 
change  the  steam-pressure,  or  else  the  speed  of  the  engine,  so  as  to 
allow  the  cut-off  to  occur  at  a  point  more  nearly  at  its  correct  position. 

Quoting  from  a  series  of  tests  which  we  have  before  us  and  which 
were  made  upon  Corliss  engines  of  medium  size,  we  find  that  the  amount 
of  condensation  and  leakage,  taken  together  up  to  the  point  of  cut-off, 
was  60  per  cent,  of  the  steam  consumed  when  the  cut-off  was  at  5  per 
cent,  of  the  stroke,  45  per  cent,  with  the  cut-off  at  10  per  cent.,  35 
per  cent,  with  the  cut-off  at  15  per  cent.,  30  per  cent,  with  the  cut-off 
at  20  per  cent.,  20  per  cent,  with  the  cut-  off  at  30  per  cent.,  and  15 
per  cent,  with  the  cut-off  at  40  per  cent. 

It  will  be  seen  from  the  above  that  the  percentage  of  loss  decreases 
as  the  point  of  cut-off  grows  later,  and  the  later  cut-off  may  cause  as 


ADIABATIC  EXPANSION  OF  STEAM  179 

much  condensation,  and  even  more,  as  with  an  early  cut-off,  owing 
to  the  large  quantity  of  steam  used  when  the  cut-off  is  late  in  the 
stroke.  It  is  evident  that  it  is  better  to  operate  an  engine  with  too 
heavy  a  load  than  with  too  light  a  load,  as  far  as  the  consumption  of 
steam  is  concerned. 

If  an  engine  is  overloaded,  the  surest  way  of  improving  the  opera- 
tion is  to  add  a  condenser,  the  gain  of  which  is  from  20  to  25  per 
cent.,  when  account  is  taken  of  the  steam-consumption  of  the  engine 
only;  but  if  measured  from  the  coal-consumption  the  gain  will  be  less, 
because  it  is  not  possible  to  heat  the  feed- water  to  so  high  a  temperature 
by  means  of  exhaust-steam  when  a  condenser  is  used  as  when  running 
non-condensing. 

STEAM-WASTE     FROM     LEAKAGE 

The  steam-leakage  past  the  valves  and  pistons  of  both  high-  and 
low-speed  engines  is  of  notable  amount;  at  high  speed  the  increase  of 
leakage,  with  the  greater  difference  of  pressure  on  each  side  of  the 
piston,  is  less  than  at  low  speed,  and  with  jacketed,  less  than  with 
non-jacketed  cylinders.  It  has  also  been  noted  that  good  lubrica- 
tion of  valves  and  cylinders  reduces  the  leakage  materially. 

In  experiments  made  to  determine  what  effect  superheating 
would  have  on  leakage  loss,  it  was  found,  as  has  been  the  case  in  some 
other  similar  experiments,  that  superheating  would  reduce  the  leak- 
age loss  about  25  per  cent.,  the  reason  being,  apparently,  that  a  less 
weight  of  superheated  steam  than  of  saturated  steam  flows  through 
a  narrow  fissure,  and  the  condensation  is  reduced. 

In  trials  with  the  valve  stationary  there  was  less  leakage  than 
when  it  was  moving;  but  when  the  valve  was  moving,  the  leakage 
became  less  as  the  speed  of  running  became  greater.  Experiments 
made  with  the  valve  stationary  in  different  positions  seem  to  show 
that  the  leakage  is  approximately  in  inverse  proportion  to  the  amount 
of  overlapping  of  the  port  and  valve;  that  is,  the  greater  the  amount 
of  overlapping  the  less  the  leakage. 

Experiments  on  the  leakage  of  steam  past  the  piston,  by  admitting 
steam  to  one  end  of  the  cylinder  and  blocking  the  port  at  the  other  end, 
and  by  weighing  the  condensation  in  the  dead  end,  showed  that  this 
leak  is  less  than  2  per  cent,  of  the  steam-consumption  of  the  engine. 


180  ADIABATIC  EXPANSION  OF  STEAM 

It  is  evident  that  with  a  valve-leakage  error  of  from  4  to  20  per  cent, 
and  a  piston-leakage  error  of  from  1  to  2  per  cent.,  experiments  on 
initial  condensation  which  do  not  take  these  factors  into  account 
will  be  misleading. 

An  unlooked-for  result  was  the  discovery  that  the  loss  due  to 
condensation  on  the  cylinder- walls  of  unjacketed  engines  diminishes 
with  a  rise  of  initial  pressure  and  temperature,  the  ratio  of  expansion 
being  constant,  and  that  this  law  holds  without  regard  to  the  speed 
of  the  engine. 


THEORETICAL     EFFICIENCY     OF      THE 
STEAM-ENGINE 

An  engine  receiving  all  its  heat  at  some  given  temperature,  and 
rejecting  the  heat  (not  lost  by  expansion)  at  some  lower  temperature, 
must,  with  its  conveyer,  pass  through  a  series  of  changes  in  pressure 
and  volume,  according  to  Carnot's  cycle,  without  loss  or  gain  of  heat 
from  outside  sources.  Such  an  engine  would  be  reversible.  No  such 
engine  can  be  constructed  or  practically  operated;  but  its  theoretical 
efficiency  serves  as  a  standard  of  comparison,  toward  which  the  modern 
ideal  design  and  construction  are  tending.  The  efficiency  of  the  per- 
fect elementary  engine  depends  only  upon  the  highest  and  lowest 
temperatures  between  which  it  is  worked,  and  is  independent  of  the 
nature  of  the  working  substance. 

rn rp 

The  following  table  has  been  computed  from  the  formula  — w~^' 

in  which  T  represents  the  absolute  temperatures  of  the  initial  and 
exhaust  steam  derived  from  their  absolute  pressures.  The  upper 
horizontal  line  contain  the  barometric  negative  pressures  due  to  the 
absolute  pressure  in  pounds  in  the  second  horizontal  line. 

A  study  of  the  above  table  will  show  approximately  the  saving 
that  may  be  effected  by  reducing  the  back  pressure  of  any  engine, 
which  in  many  cases  is  ignored  because  the  effect  is  not  readily  seen. 
It  has  been  observed,  in  trials,  that  the  back  pressure  may  be  as  great 
as  3  or  more  pounds  above  atmospheric  pressure  from  the  use  of 
long  or  small  exhaust-pipes,  many  elbows,  defective  valve-movement, 
or  small  ports  or  steam-passages  in  the  cylinder. 


ADIABATIC  EXPANSION  OF  STEAM 


181 


TABLE  XXIX. — THEORETICAL  HEAT-EFFICIENCY  OF  A  PERFECT  STEAM-ENGINE 
AT  VARIOUS  ABSOLUTE  INITIAL  AND  BACK  PRESSURES,  SHOWING  PERCENTAGE 
OF  EFFICIENCY. 


Initial 
pressure, 
absolute. 

27.88 

25.85 

23.83 

21.78 

19.74 

17.70 

13.63 

9.56 

5.49 

n         +3.3 

Ibs. 

+  5.3 

Ibs. 

1 

2 

3 

4 

5 

6 

8 

10 

12 

14.7 

18 

20 

60 

25.3 

22.1 

20.1 

18.5 

17.3 

16.3 

14.6 

13.2 

12VO 

10.7 

9.3 

8.6 

70 

26.3 

23.1 

21.2 

19.6 

18.4 

17.4 

15.7 

14.4 

13.2 

11.9 

10.5 

9.8 

80 

27.2 

23.4 

22.1 

20.6 

19.4 

18.4 

16.7 

15.4 

14.2 

12.9 

11.6 

10.9 

90 

28.0 

24.8 

22.8 

21.4 

20.2 

19.2 

17.6 

16.2 

15.1 

13.8 

12.5 

11.8 

100 

28.6 

25.6 

23.6 

22.2 

21.0 

20.0 

18.4 

17.1 

16.0 

14.7 

13.4 

12.7 

110 

29.3 

26.2 

24.3 

22.8 

21.6 

20.7 

19.1 

17.8 

16.7 

15.4 

14.1 

13.4 

120 

29.8 

26.8 

24.9 

23.4 

22.3 

21.3 

19.7 

18.4 

17.4 

16.1 

14.8 

14.1 

130 

30.4 

27.4 

25.4 

24.1 

23.0 

22.0 

20.4 

19.1 

18.1 

16.8 

15.5 

14.8 

140 

30.9 

27.8 

26.0 

24.6 

23.5 

22.5 

20.9 

19.6 

18.6 

17.3 

16.1 

15.4 

150 

31.3 

28.3 

26.4 

25.0 

23.9 

22.9 

21.3 

20.1 

19.1 

17.8 

16.5 

15.9 

175 

32.4 

29.2 

27.6 

26.2 

25.1 

24.1 

22.6 

21.4 

20.3 

19.1 

17.8 

17.2 

200 

33.2 

30.3 

28.6 

27.2 

26.0 

25.1 

23.6 

22.4 

21.3 

20.1 

18.9 

18.3 

225 

34.0 

31.2 

29.4 

28.0 

26.9 

25.9 

24.5 

23.3 

22.2 

21.1 

19.9 

19.2 

250 

34.8 

32.0 

30.1 

28.8 

27.7 

26.8 

25.4 

24.1 

23.1 

22.0 

20.8 

20.1 

275 

35.4 

32.6 

30.8 

29.5 

28.4 

27.5 

26.1 

24.9 

23.8 

22.7 

21.5 

20.9 

300 

35.9 

33.2 

31.4 

30.1 

29.1 

28.2 

26.7 

25.6 

24.5 

23.4 

22.2 

21.6 

For  a  back  pressure  of  3  pounds  the  loss  in  efficiency  may 
be  1.3  per  cent,  at  ordinary  initial  pressures,  more  at  low  pressures, 
and  less  at  the  high  pressures;  but  when  condensation  and  its  value 
are  considered,  the  saving  is  very  much  more  apparent,  and  becomes 
a  strong  plea  in  favor  of  the  use  of  compound  condensing-engines 
wherever  it  is  possible  to  operate  them.  Since  surface-condensers 
have  become  so  perfected  and  water-cooling  towers  available,  the 
compound  condensing-engine  has  become  of  the  first  consideration 
in  the  instalment  of  factory  and  electric  power. 


ACTUAL     EFFICIENCY 

The  actual  efficiency  of  any  type  of  steam-engine  has  been  usually 
derived  from  the  number  of  pounds  of  steam  used  per  hour,  or  of  water 
fed  to  the  boiler,  divided  by  the  horse-power.  Thus,  an  ordinary 
engine,  using  500  pounds  of  water  per  hour  and  developing  15  in- 

500 

dicated  horse-power,  will  consume —-  =  33.3  pounds  per  horse-power 

lo 

hour.     As  a  horse-power  corresponds  to  the  development  of  33,000 


182  ADIABATIC  EXPANSION  OF  STEAM 

foot-pounds  per  minute,  and  as  778  foot-pounds  is  the  equivalent  of 

33  000 
one  thermal  unit,  then       '      -  =  42.42  units  per  horse-power,  which 

77o 

may  be  a  constant  for  obtaining  the  thermal  efficiency  of  the  engine, 

42.42 

and  -r-~  -  minute  =  thermal  efficiency. 

thermal  units  per  horse-power 

Then,  for  example,  with  a  simple  engine  running  with  an  initial 
pressure  of  75.3  by  gauge,  and  exhausting  at  atmospheric  pressure, 
the  formula  for  the  thermal  units  per  pound  will  be 
(23)  .  .  xr  +  qi  —  q2,  in  which  x  =  the  percentage  of  moisture  in  the 
steam;  r  =  the  latent  heat  in  the  steam;  qi  =  the  units  of  heat  in  the 
water  at  the  initial  pressure,  and  q2  =  the  units  of  heat  in  the  water 
at  atmospheric  pressure  or  at  exhaust-pressure. 

Using  the  values  in  the  formula,  we  have  :  .98  X  888.4  +  291  .2  -  180.9 

980.9x33.3  pounds 
=  980.9  thermal  units  per  pound;   then  -  J          —  =  544.4 

thermal   units    per    minute,    and    the    thermal    efficiency   will     be 
42'42 


5444 

The  best  record  that  we  have  for  multicompound  condensing- 
engines  is  for  about  200  thermal  units  per  horse-power  minute,  which 

42  42 
shows  a  thermal  efficiency  of  -^—  =  .  212;  and  with  superheating  there 


are  possibilities  of  from  10  to  20  per  cent,  additional  thermal  efficiency 
in  the  use  of  steam  and  a  saving  of  from  6  to  8  per  cent,  in  coal-con- 
sumption, depending  upon  the  method  of  obtaining  the  superheat. 

COMPRESSION     AND     BACK     PRESSURE 

From  a  perusal  of  the  large  amount  of  discussion  which  has  per- 
vaded the  technical  journals  of  late  years,  the  economical  value  and 
use  of  compression  seem  to  be  very  much  tangled,  although  its 
mechanical  value  is  generally  conceded  by  the  evidence  of  its  useful- 
ness as  shown  in  actual  trials,  in  which  it  has  been  found  indispensable 
in  high-speed  engines  with  a  graduation  due  to  the  degree  of  speed. 

Its  economy  of  steam  and  power  seems  to  be  the  principal  field  of 
discussion,  from  which  the  facts  should  decide  the  points  at  issue. 
As  its  mechanical  effect  upon  the  momentum  of  the  moving  parts  of 


ADIABATIC   EXPANSION  OF  STEAM  183 

an  engine  to  the  extent  of  producing  its  silent  action  at  various  speeds 
is  obvious,  it  only  needs  the  computed  amount  formulated  from  the 
experience  of  trials. 

The  principal  facts  shown  by  the  indicator-card  are  that  the  clear- 
ance- and  steam-passages  must  be  filled,  for  each  stroke  of  the  piston, 
with  a  volume  of  steam  equal  to  the  total  clearance,  less  the  exhaust- 
pressure;  which  adds  3  per  cent,  to  the  mean  effective  pressure  at 
J  cut-off  and  5  per  cent,  clearance.  Then  the  total  value  of  the 
clearance-volume  at  \  cut-off  being  but  3  per  cent,  of  the  mean 
effective  pressure  and  the  clearance  5  per  cent,  of  the  stroke,  the  loss 
of  steam  due  to  clearance  will  be  -f^  =  16  per  cent,  loss,  and  16  —  3  per 
cent,  gain  in  power  equals  13  per  cent,  loss  due  to  clearance. 

On  the  other  hand,  if  compression  is  carried  up  to  the  initial 
pressure  of  say  100  pounds,  the  heat  generated  by  compression  will 
raise  the  temperature  of  the  compressed  exhaust  from  213°  to  above 
600°  F.,  or  about  260°  above  the  temperature  of  the  initial  steam, 
the  superheat  of  which  will  be  given  to  the  cylinder-walls  of  the  cut- 
off and  clearance-space.  The  back  pressure  due  to  compression  will 
be  fully  compensated  by  the  expansion  of  the  accumulated  pressure 
behind  the  piston  for  the  next  stroke,  and  the  clearance-volume  of 
initial  steam  will  be  saved.  This  should  hold  as  a  proportion  for  any 
degree  of  compression. 

As  excessive  compression  is  not  needed  for  counteracting  the 
momentum  of  the  moving  parts  for  smooth  running,  a  noted  builder 
of  high-speed  engines  assumes  that  for  130  revolutions  per  minute, 
24-inch  stroke,  compression  should  commence  at  9  per  cent,  from 
the  terminal  of  the  stroke;  for  160  revolutions  per  minute,  24-  inch 
stroke,  12  per  cent. ;  and  for  240  revolutions  per  minute,  16-inch  stroke, 
19  per  cent. 

The  author  suggests  that  a  more  equable  ratio  of  compression  for 
balancing  momentum  would  be  derived  from  the  equation : 


/OA\  A  /      rev.  pr.  m.  ,,      £  .     .     , 

(24)     .     .     A/ —     —i — : — - —  =  length  of  compression  in  inches. 
r    stroke  in  inches 

This  may  not  answer  fully  for  the  difference  in  weight  of  the 
moving  parts  as  designed  by  different  builders  and  for  different 
pressures. 

Of  late  years  there  has  been  much  discussion  in  regard  to  the 


184  ADIABATIC  EXPANSION   OF  STEAM 

economy  of  compression  and  also  as  to  its  mechanical  value.  This 
discussion,  and  the  arguments  advanced  for  and  against  compression, 
have  as  yet  proved  nothing,  and  experiments  so  far  made  have 
shown  such  discordant  results  as  to  cause  distrust  in  their  methods. 

Experiments  in  Belgium  and  Germany  have  shown  a  marked  falling 
off  in  efficiency  with  heavy  compression,  the  difference  amounting  in 
one  case  to  an  increase  of  50  per  cent,  in  the  steam-consumption. 

For  instance,  the  experiments  of  Professor  Dwelshauvers-Dery,  at 
Liege,  showed,  as  the  compression  was  increased  from  10  up  to  30 
per  cent.,  an  increase  of  21  per  cent,  in  the  steam-consumption,  and 
for  a  further  rise  of  40  per  cent,  compression  an  increase  of  50  per 
cent,  in  the  steam  used  over  that  with  no  compression.  On  the  other 
hand,  careful  experiments  at  Stevens  Institute  and  at  Cornell  Univer- 
sity show  only  a  slight  change  in  the  steam-consumption  accom- 
panying increased  compression. 

It  is  difficult  to  believe  that  any  such  difference  as  that  shown  by 
the  European  experiments  could  result  from  so  slight  a  cause.  The 
only  loss  that  can  result  from  an  increase  of  compression  is  the  loss  of 
work  shown  by  the  rounding  of  the  heel  of  the  diagram,  which  is 
largely  offset  by  the  decrease  in  the  amount  of  fresh  steam  required 
to  fill  the  clearance  up  to  the  initial  pressure.  There  is  some  con- 
densation of  the  cushion-steam,  but  this  helps  to  warm  up  the  cylinder 
and  piston-ends  and  to  diminish  the  initial  condensation. 

THE     ECONOMY     OF     HIGH-PRESSURE     STEAM 

The  economy  due  to  high  pressure  has  been  slowly  developed  in 
practice  by  its  gradual  increase  for  power  during  the  latter  part  of 
the  nineteenth  century;  so  that  the  general  limit  of  50  to  60  pounds 
rose  to  80,  100,  and  even  to  160  pounds  for  special  purposes  in  a  single 
cylinder;  and  for  multiple  expansions,  150  to  200  pounds,  which  is 
probably  nearing  its  practical  limit,  although  250  pounds  was  ex- 
ploited many  years  since  in  single  cylinders  by  Perkins,  in  England, 
with  practical  failure,  and  1,000  pounds  was  used  in  a  steam-gun  of 
Perkins's  design  by  the  author  sixty  years  ago  in  New  York,  which 
proved  a  practical  failure  for  that  purpose. 

A  standard  boiler  is  assumed  to  evaporate  34.5  pounds  of  water 
per  hour  from  and  at  212°  F.  at  atmospheric  pressure,  to  indicate  a 


ADIABATIC  EXPANSION   OF  STEAM  185 

boiler  horse-power.  This  rate  of  evaporation  is  approximately  used 
for  the  relative  size  of  a  boiler  for  the  required  consumption  of  steam 
per  horse-power  in  any  engine.  The  actual  evaporation  at  higher 
pressures  is  less  by  a  small  percentage,  for  its  rating  for  at  75  pounds 
pressure  it  is  33.85  pounds,  and  at  150  pounds  it  is  32.89  pounds. 

The  weight  of  steam  per  cubic  foot  increases,  in  a  far  greater  ratio 
in  a  rising  pressure  than  is  due  to  the  decrease  in  boiler-evaporation, 
being  .0380  pound  at  atmospheric  pressure,  .208  pound  at  75  pounds 
gauge,  and  .367  pound  per  cubic  foot  at  150  pounds  gauge-pressure; 
inversely,  the  relative  volumes  vary  greatly  from  1,646  cubic  feet  per 
pound  at  atmospheric  pressure — which  is  valueless  as  a  power  from 
pressure  alone — to  299  cubic  feet  per  pound  at  75  pounds  pressure, 
and  169  cubic  feet  per  pound  at  150  pounds  pressure. 

With  any  given  single-cylinder  engine  using  steam  at  75  pounds, 
cutting  off  at  yV  with  5  per  cent,  clearance,  the  quantity  of  steam 
used  per  cubic  foot  of  cylinder- volume  will  be  .208 X. 4  =  .0832  pound 
per  cubic  foot,  with  a  mean  effective  pressure  of  58.6  pounds  and 
terminal  of  25  pounds  absolute.  For  the  same  cylinder  using  steam 
at  150  pounds,  cutting  off  at  yV  with  5  per  cent,  clearance,  the 
quantity  of  steam  used  per  cubic  foot  of  cylinder-volume  will  be 
.367 X.I  =  .0367  pound,  with  a  mean  effective  pressure  of  58.8  pounds 
and  terminal  of  8.4  pounds  absolute,  thus  obtaining  a  saving  in  steam 
of  56  per  cent,  for  the  same  power.  The  saving  in  boiler-capacity 
and  fuel  will  approximate  this  proportion.  In  ordinary  practice  these 
figures  may  not  be  reached,  but  a  great  saving  has  been  proved  under 
practical  conditions. 

The  losses  and  gains  in  economy  of  the  use  of  steam  are  well  illus- 
trated by  the  following  diagrams.  In  Fig.  142  is  shown  the  loss  by 
decrease  in  the  ratio  of  expansion. 

•The  solid  outline  represents  the  work-area  due  to  expansion  of 
steam  when  the  cut-off  occurs  at  half-stroke.  That  is,  gm  =  2ga,  or 
the  number  of  expansions  is  two.  If,  now,  the  number  of  expansions 
is  increased  to  three,  so  that  gn  =  3ga,  then  there  is  added  an  area 
bcdf,  shown  in  dotted  outline,  which  represents  an  extra  amount  of 
work  obtained  without  increasing  the  quantity  of  steam  used,  since 
there  is  no  alteration  of  the  volume  of  steam  previous  to  cut-off. 

For  example,  at  100  pounds  absolute  initial  pressure,  with  50  per 


186 


ADIABATTC  EXPANSION  OF  STEAM 


cent,  cut-off,  the  mean  effective  pressure  will  be  84.6  pounds  for  two 
expansions;  if  expanded  three  tunes,  the  mean  effective  pressure  will  be 


FIG.  142. — Loss  in  expansion. 

69.9  pounds,  with  50  per  cent,  more  work  at  the  reduced  mean  effective 

84  6 
pressure,  or  as  84.6  is  to  69.9  +  34.9;  then  —-—  =  .807,  or  nearly  20 

per  cent,  more  work  for  the  same  volume  of  steam. 

Manifestly,  then,  the  increase  of  ratio  of  expansion  has  made  a 
greater  amount  of  work  available  from  the  amount  of  steam  used, 


wMMMMMMMMll/Ml/m 

FIG.  143. — Higher  pressure  and  the  vacuum. 

and  it  is  evident  that  the  greater  the  ratio  the  larger  becomes  the  ad- 
ditional area  bcdf,  and  consequently  the  less  the  steam-consumption 
per  unit  of  power  developed. 

The  ratio  of  expansion  may  be  increased  by  increasing  the  initial 
pressure  and  shortening  the  cut-off.     The  final  volume  will  thus 


ADIABATIC   EXPANSION   OF  STEAM 


187 


remain  the  same,  but  the  initial  volume  will  be  less  than  before,  and 
consequently  the  number  of  expansions  will  be  greater. 

Fig.  143  represents  an  indicator-diagram  from  one  end  of  a  simple 
non-condensing  engine.  Suppose  that  the  pressure  is  increased  12 
pounds,  and  cut-off  shortened  so  that  exhaust  will  occur  at  the  same 
pressure  as  before.  Then  the  steam-line  will  be  raised  to  the  shaded 
position  and  an  extra  amount  of  work  will  be  obtained,  represented 
by  the  area  shaded  with  double  cross-section  lines.  If,  on  the  contrary, 
the  initial  pressure  be  left  unchanged  and  a  condenser  added,  so  that 
the  back  pressure  is  reduced  12  pounds,  then  the  area  representing 


ao 

18 
£     16 

I- 

0|     12 

W 

~     10 

t: 

4 
2 


75  150  225  300  375 

FIG.  144. — Ideal  and  actual  curves. 


450 


increased  work  will  be  that  shown  by  plain  cross-sectioning.  A 
comparison  of  the  two  areas,  which  are  to  the  same  scales,  makes 
plain  the  gain  to  be  derived  from  reducing  the  back  pressure  in  a 
non-condensing  engine,  rather  than  by  increasing  the  initial  pressure. 

To  illustrate  further  the  economy  of  the  use  of  steam  at  high 
pressure,  the  diagram  (Fig.  144)  shows  the  relation  of  the  ideal  and 
actual  curves  with  the  steam-consumption  at  varying  pressures  in 
condensing-engines. 

The  curve  shown  solid  is  for  the  ideal  engine,  and  consequently 
is  practically  valueless,  inasmuch  as  it  does  not  pertain  to  actual 
results  obtained.  But  it  does  show  what  the  perfect  engine  might 
accomplish,  and  it  thus  forms  a  basis  of  comparison  for  results 


188 


ADIABATIC  EXPANSION  OF  STEAM 


which  have  been  secured  in  practice.  The  curve  shown  dotted  is 
plotted  from  the  results  of  tests  made  upon  actual  engines  at  various 
steam-pressures,  the  results  showing  highest  economy  being  taken 
in  plotting  the  curve.  As  can  be  seen,  the  actual  curve  approaches 
the  ideal  as  the  pressure  rises,  indicating  that  as  the  pressure  is  in- 
creased the  economy  of  the  actual  engine  approaches  more  nearly 
that  of  the  ideal  engine. 

THE     MOST     ECONOMICAL     POINT     OF     CUT-OFF 

This  was  a  much-discussed  question  a  few  years  since,  and  the 
cut-off  was  claimed  to  be  equal  to  the 

absolute  back  pressure 
absolute   initial  pressure7 

but  as  nothing  was  proposed  in  regard  to  the  effect  of  the  clearance 
in  this  formula  it  should  be  added  to  give  the  real  cut-off.  For  ex- 


E 
I20 

•s 

•o 

c 

3 


\  t 


30 


U 


0.1        0.2       0.3       0.4      0.5      0.6       0.7      0.8       0.9      1.00 

Cut-off  in  Fractions  of  Stroke 

FIG.  145. — Diagram  of  economical  cut-off. 

ample,  an  initial  pressure  of  90  pounds  and  terminal  pressure  of  1 

15  7 
pound  by  gauge;  this  would  be  — —  =  .15  cut-off,  which  would  give 

a  mean  engine-pressure  of  44  pounds  without  clearance,  and  52  pounds 
with  10  per  cent,  clearance,  with  a  corresponding  increase  of  steam 
equal  to  a  20-per-cent.  cut-off  without  clearance. 


ADIABATIC  EXPANSION  OF  STEAM  189 

The  experiments  of  Professor  Den  ton  show  a  larger  cut-off  for 
the  above  conditions  by  a  possible  addition  of  the  clearance  to  the 
theoretical  cut-off  as  above  given. 

In  Fig.  145  is  a  diagram  of  the  curves  showing  the  most  eco- 
nomical cut-off  at  different  pressures  and  the  consumption  of  steam 
corresponding  with  the  cut-off.  The  engine  was  a  17  X  30-inch  non- 
condensing,  double-valve  type,  with  clearance  stated  to  be  large. 

In  the  diagram  the  vertical  lines  represent  the  cut-off,  and  the 
horizontal  lines  the  pounds  of  steam  consumed  per  effective  horse- 
power. The  intersection  of  the  curves  with  the  vertical  lines  shows 
the  variation  of  the  weight  of  steam  for  each  advance  in  the  point  of 
cut-off.  It  will  be  seen  from  tracing  the  curves  that  the  best  result 
for  30  pounds  pressure  was  obtained  at  about  -^£Q  cut-off,  that  for 
60  pounds  at  about  -£/-$  cut-off,  and  that  for  90  pounds  at  about 
-f/Q  cut-off.  For  a  short  distance  each  side  of  these  points  of  cut- 
off the  economy  shows  but  little  variation,  and  that  with  increasing 
pressure  the  point  of  economical  cut-off  has  an  inverse  decreasing  ratio. 

From  these  and  other  experiments  a  formula  has  been  deduced 
for  approximately  the  most  economical  cut-off  for  a  non-condensing 

100 
simple  engine,  in  which  the  cut-off  = -=,  in  which  P  is  the  initial 

gauge-pressure,  or  above  the  atmospheric,  and  above  a  vacuum  for  a 
condensing-engine. 

The  cut-off  in  a  single-cylinder  engine  is  limited,  by  an  initial 
gauge-pressure  of  about  110  pounds  with  5  per  cent,  clearance,  to  a 
minimum  of  one-fifth  of  the  stroke  for  economic  effect,  as  in  this  case 
the  terminal  pressure  will  be  but  1  pound  above  atmospheric  and  will 
about  equalize  engine-friction. 


CHAPTER    XIII 


THE   INDICATOR   AND    ITS   WORK 

THE  means  of  knowing  what  are  the  steam  conditions  within  the 
cylinder  of  an  engine  is  a  most  important  one  to  all  concerned  in  the 
operation  of  steam-power. 

The  interpreter  is  found  in  the  indicator,  a  recorder  of  the  varying 
pressures  within  the  cylinder  from  which  the  action  of  the  valves 
and  valve-gear  is  noted  upon  sight,  and  by  means  of  which  the  value 
of  the  steam  used  is  made  a  matter  of  rapid  computation. 

The  indicators  in  use  are  of  several  patterns,  all  made  on  the 
same  general  principle,  namely,  a  light-moving  piston,  pressed  by  the 

steam  against  a  delicate 
and  accurately  gauged 
spring,  operating  a  light 
parallel-motion  device, 
which  marks  the  lines 
of  pressure  by  a  pencil 
on  a  paper  moved  too 
and  fro,  and  which  is 
placed  upon  a  cylinder 
and  actuated  by  the 
motion  of  the  pis- 
ton within  the  engine- 
cylinder. 

In  Fig.  146  we  illus- 
trate one  of  the  latest 
patterns  of  an  indicator 

having  a  light  aluminum  reducing-wheel  attached  directly  to  the 
diagram-drum.  The  reducing-wheel  has  a  number  of  bushings  for 
its  upper  section,  of  sizes  to  equalize  the  length  of  diagram  or  card  to 
any  length  of  piston-stroke.  This  method  of  reducing  the  piston- 
190 


FIG.  146. — Indicator  and  reducing-wheel. 


THE  INDICATOR  AND  ITS   WORK 


191 


stroke  of  the  engine  is  so  neat,  complete,  and  accurate  that  we  forego 

illustration  of  the  many  awkward  reduction-devices  in  use. 

In  Fig.  147  are  shown  the  details  of  the  construction  of  the  Lip- 

pincott    indicator.     It 

will    be    noted    that 

the    indicator-cylinder 

is  steam-jacketed,  with 

steam-inlets  below  the 

piston  so  that  the  cylin- 
der and  piston  temper- 
atures are  always  the 

same  and  are  also  un- 
der the  same  pressure 

—a    great    advantage 

when  indicating  under 

high  pressures. 

A  special  feature  in 

its  construction  is  the 

free-moving    piston, 

which  has  a  guide-rod 

to   which   it   is    fixed, 

with    bearings   at   the 

top  of  the  spring  and 

in  the  cylinder  beneath  the  piston,  giving  a  perfect  and  free  lineal 
motion  to  the  piston  and  being  practically 
frictionless.  The  piston-area  is  usually  exactly 
J  inch  for  use  up  to  100  pounds  pressure,  with 
springs  of  60,  50,  and  40  pounds  per  inch  of 
height  in  the  card,  while  the  high-pressure  piston- 
area  is  exactly  £  inch,  and  is  suitable  for  indi- 
cating up  to  200  pounds  pressure  with  the  No. 
60  spring. 


FIG.  147. — Lippincott  indicator. 


FIG.  148. — High-press- 
ure piston. 


THE     ALUMINUM     R  E  D  U  C  I  N  G  -  W  H  E  E  L 

It  is  unnecessary  to  go  into  the  relative  merits 
of  the  reducing- wheel  versus  the  pendulum, 
lazy-tongs,  pantagraph,  etc.,  as  the  superiority 


192 


THE  INDICATOR  AND  ITS  WORK 


of  a  good  wheel  over  these  antiquated  devices  is  conceded  by  all 
up-to-date  engineers.  We  admit  that  some  reducing-wheels  give  so 
much  trouble  from  disarrangement  of  cords,  breakage  of  springs, 
and  excessive  wear  that  some  engineers  have  gone  back  to  the 
old  methods;  but  we  have  yet  to  learn  of  a  case  where  a  user  of 
the  aluminum  wheel  has  discarded  it.  By  the  aid  of  this  wheel 
directly  connected  to  the  indicator  it  is  possible  to  indicate  several 
different  engines  in  a  day;  but  we  have  known  of  hours  being  con- 
sumed in  securing  material  for,  and  rigging  up,  a  pendulum,  and  often 
with  inaccurate  results. 

The  general  design  of  the  wheel  is  shown  in  Fig.  146.  It  is  com- 
pact, and  at  the  same  time  has  not  been  made  so  small  that  it  is 
subjected  to  rapid  wear  by  use,  or  so  that  its  application  to  long- 
stroke  engines  will  seriously  tax 
its  capacity. 

The  main-cord  wheel  is  made 
of  aluminum,  turned  inside  and 
out,  and  perfectly  balanced.  This 
wheel  is  capable  of  operating  on 
strokes  as  high  as  7\  feet,  or  more, 
but  by  substituting  a  smaller  pul- 
ley it  becomes  suitable  for  short 
strokes  and  high  speeds,  its  range 
then  being  from  6  to  24  inches. 

The  spring-case  spindle  ex- 
tends through  the  case,  and  is 

provided  with  a  coarse  square  thread,  eight  to  the  inch,  upon  which  is 
a  suitably  shaped  composition-nut,  to  which  is  attached  the  guide- 
pulley  arm. 

Each  revolution  of  the  main-cord  wheel  moves  the  guide-pulley 
across  the  face  of  the  wheel  about  TV  inch,  so  that  the  main  cord  is 
guided  perfectly  on  the  wheel,  no  matter  in  what  direction  it  is  led. 

The  setting  of  an  indicator  is  an  important  matter  when  accurate 
results  are  sought.  The  point  most  desired  is  to  have  a  quick  transit 
of  the  pressure  in  the  cylinder  to  the  piston  of  the  indicator,  and 
for  this  purpose  the  indicator  should  be  attached  directly  to  the 
clearance-space,  of  the  cylinder  without  piping,  elbows,  or  cocks, 


FIG.  149. — Close-connected  indicators. 


THE   INDICATOR  AND  ITS  WORK 


193 


FIG.  150. — Cross-pipe  connection. 


save  the  one  on  the  indicator.  This  is  most  desirable  on  high-speed 
engines,  as  shown  in  Fig.  149;  but  as  this  needs  two  indicators,  the 
usual  way  for  a  single  indicator  is  to  connect  the  clearance-spaces  with  a 
cross-pipe,  with  the  indi- 
cator in  the  centre,  as 
shown  in  Fig.  150.  When 
the  connecting-pipes  are 
desired  to  be  retained, 
the  angle-cocks  at  each 
end  are  needed  to  lessen 
the  clearance.  In  this 
case,  with  long-stroke 
engines  the  cross-pipe 
should  be  one  size  larger 
than  the  thread  of  the 
indicator-cock ;  but  a 
better  way  is  to  use  two 
indicators. 

A  too  long  pipe-con- 
nection or  a  too  small  one  produces  freak  cards,  which  do  not  represent 
the  true  action  of  the  steam  within  the  cylinder.     On  Corliss  and  other 

four-valve  engines  the  in- 
dicator is  attached  at  the 
side  of  the  cylinder,  as 
shown  in  Fig.  151.  In 
connections  to  vertical 
cylinders  care  should  be 
J)  had  to  prevent  water  from 
filling  the  indicator-con- 
nection, as  it  tends  to  pro- 
duce a  freak  card  for  the 
lower  end  of  the  cylinder. 
When  a  pendulum  or 
pantagraph  reducing-gear 

Fio.  151.-Side  connection.  is  employed  a  light  and 

very  flexible  spring  may 

be  used  to  advantage  to  keep  the  cord  uniformly  taut.     An  arrange- 
ment of  this  kind  is  shown  in  Fig.   152,  in  which  a  loop  or  hook 


194 


THE  INDICATOR  AND  ITS  WORK 


attached  to  the  cord  may  be  extended  by  a  light  cord  to  a  spring  at 
the  side  of  the  cylinder  or  engine-frame — a  needed  arrangement  for 
high-speed  engines. 


FIG.  152. — Slack-spring  attachment. 

Indicators  are  made  right-and-left-hand,  or  with  adjusting  parts1 
to  make  the  same  instrument  set  both  ways,  as  will  be  seen  in  Fig. 

153,  in  which  the  pencil- 
holder  may  take  the  pen- 
cil in  opposite  directionsr 
the  stop-screw  being 
changed  from  one  to  the 
other  side  of  the  arm, 
and  the  drum  shifted  to- 
notches  provided  for  the 
change. 

The  details  for  oper- 
ating the  various  makes 
of  indicators  are  sent 
with  the  indicators,  and 
much  of  their  mechanism 
becomes  apparent  to 
engineers  on  inspection. 
The  pencil  should  be 
hard  and  sharp  and  the  paper  hard,  cold-pressed  letter-sheet  or 
bond-paper,  which  gives  a  good  marking  with  the  lightest  pressure 
of  the  pencil-arm. 


FIG.  153. — Right-  and  left-hand  indicator. 


THE  INDICATOR  AND  ITS  WORK 


195 


MEASUREMENT     OF     THE     I  N  D  I  C  A  T  O  R  -  C  A  R  D 

The  method  of  measuring  the  mean  engine-pressure  from  the  in- 
dicator-diagram is  shown  in  the  double  card  (Fig.  154),  which  is  the 
usual  way  for  taking  the  card  for  both  forward  and  back  strokes.  To 
lay  off  the  diagram  for  measurement,  run  off  on  the  straight  edge  of 
a  piece  of  paper  with  a  dividers,  eleven  spaces  that  will  overrun  the 
length  of  the  diagram.  Draw  vertical  lines  at  both  ends  of  the  diagram 
and  two  lines  below  it,  parallel  with  the  atmospheric  line,  for  a  register 
of  the  measurement.  Lay  the  scale  diagonally  across  the  diagram, 
as  shown  in  the  illustration,  at  an  angle  that  will  just  divide  the  end- 
spaces  over  the  vertical  lines  at  each  end  of  the  diagram;  then  mark 


H.  356.5  C.  356. 

35.625 

B.P.  .3. 

M.  32.625 


FIG.  154. — Diagram  lay-out. 

with  a  point  or  pencil  on  the  diagram  the  ten  divisions  on  the  scale, 
and  draw  vertical  lines  across  the  marks,  continuing  them  over  the 
outside  register-spaces.  Then  proceed  to  measure,  with  the  scale 
corresponding  with  the  indicator-spring,  between  the  steam-  and  ex- 
pansion-lines and  the  exhaust  line  and  compression  line.  Enter  the 
amounts  under  the  heads  H  and  C  in  the  columns  below.  Divide 
their  sums  by  10  for  the  mean  forward  pressure  of  head-  and  crank- 
ends,  and  equalize  for  their  combined  mean  forward  pressure,  less  the 
back  pressure;  from  which  the  horse-power  may  be  computed,  arid 
from  the  established  point  of  cut-off  the  steam-consumption  may  be 
found,  as  described  in  previous  sections  of  this  work.  See  "Com- 
pression" and  "Steam  Used  per  Horse-Power." 


196 


THE  INDICATOR  AND   ITS  WORK 


THE       PLANIMETER       AND      THE      MEASUREMENT      O^ 
THE      INDICATOR-DIAGRAM 

The  most  perfect  measurement  of  the  area  and  mean  pressure  of 
an  indicator-diagram  may  now  be  made  by  the  use  of  the  planimeter 
which  has  been  perfected  in  all  its  details. 

In  Fig.  155  is  shown  the  Amsler  planimeter,  which  consists  of 
two  legs  jointed  with  points  at  their  ends,  one  of  which  is  fixed,  and 

the  other,  the  tracer,  is  moved 
over  the  diagram  in  the  same 
direction  as  the  indicator- 
pencil.  At  their  juncture  is  a 
small  shaft  with  a  sharp-edged 
disk,  a  cylindrical  section  with 
a  graduated  scale  read  from  a 
fixed  vernier  scale.  A  worm- 
screw  and  index-wheel  indi- 
cate the  number  of  revolutions  of  the  rolling  disk.  To  operate  this  pla- 
nimeter, set  the  stationary  point  at  any  position,  so  that  the  tracing- 
point  can  be  carried  around  the  line  of  the  diagram  without  bringing 
the  wheel  in  contact  with  the  paper  on  which  the  diagram  is  traced — 
preferably  so  that  the  leg  with  the  tracer  in  moving  around  the  dia- 
gram will  cover  an  angular  space 
between  30  and  90  degrees  from 
the  stationary  pointer-leg. 

For  the  mean  effective. pressure 
divide  the  area  as  indicated  by  the 
scale  by  the  length  of  the  diagram 
in  inches,  and  multiply  the  quotient 
by  the  scale  of  the  spring  used  in 
the  indicator. 


FIG.  155. — Amsler  planimeter. 


FIG.  156. — Lippincott  planimeter. 


One  of  the  models  of  the  Lippincott  planimeter  is  shown  in  Fig. 
156,  in  which  R  is  the  stationary  point;  T  the  tracer;  c  a  smooth, 
round  arm  on  which  a  scale  is  laid  off;  D  a  disk  with  a  free  motion  on 
the  scaled  arm.  The  traverse  of  the  wheel  on  the  scale  indicates 
the  area. 

In  Fig.  157  is  shown  the  Lippincott  simplex  planimeter  in  position 


THE  INDICATOR  AND  ITS  WORK 


197 


for  tracing  the  area  of  an  indicator-diagram.  This  model  eliminates 
any  possible  error  due  to  the  looseness  of  the  traversing-wheel  in  Fig. 
156,  inasmuch  as  the  wheel  is  fixed  on  a  small  shaft  which  travels 
under  roller-bearings  at  either  end  of  the  frame;  so  that  the  plane  of 
the  wheel  is  rigidly  at  right  angles  to  its  axis  and  therefore  registers 
without  error. 

To  use  the  simplex  planimeter  a  large  sheet  of  smooth  cardboard 
should  be  obtained  and  the  instrument  placed  on  the  diagram,  about 
as  shown  in  the  figure,  with  the  tracer-point  B  at  either  of  the  points 


FIG.  157. — Simplex  planimeter. 

X,  and  the  wheel  W  about  f  inch  from  the  body  of  the  instrument 
(this  distance  is  not  important,  only  that  the  wheel  must  not  strike 
the  frame  at  either  extreme  of  its  travel). .  The  position  of  the  pivot- 
point  F  should  be  particularly  noticed,  the  angle  of  the  arm  being 
somewhat  greater  than  a  right  angle. 

While  the  planimeter  is  held  in  the  position  shown  in  the  figure,  a 
slight  pressure  on  the  wheel  W  makes  an  indentation  in  the  paper 
which  is  easily  seen.  The  diagram  is  then  traced  in  the  direction  of 
the  arrows,  until  the  tracing-point  returns  to  the  starting-point  X, 
and  while  in  this  position  the  wheel  W  is  again  pressed  in  the  paper, 
thereby  leaving  two  indentations.  The  distance  between  these, 
measured  by  a  scale  of  the  same  dimensions  as  that  of  the  indicator- 
spring — a  60  scale  for  a  60  spring — gives  the  mean  effective  pressure 
direct  and  accurately.  For  the  mean  effective  pressure  direct,  the 


198 


THE  INDICATOR  AND   ITS   WORK 


tracer-bar  should  be  extended  until  the  points  A  and  B  are  the  same 
distance  apart  as  the  extreme  length  of  the  diagram.     If  the  reading 

is  desired  in  square  inches 
and  tenths,  the  points 
A  and  B  should  be  set 
6  inches  apart  and  a  60 
scale  used  for  reading  the 
area  in  square  inches  and 
tenths. 

The  three  positions  of 
the  planimeter,  shown  in 
Fig.  158,  are  those  as- 
sumed during  the  tracing 
of  the  diagram. 

No  attention  need  be 
given  to  the  movement  of 
the  wheel  while  the  card 
is  being  traced,  except 
that  the  wheel  is  clear 
from  the  frame  by  f  inch 
at  the  start,  B,  and  does 
not  run  against  the  other 
end  of  the  frame  at  the 
finish,  D,  by  an  extra  large 
diagram.  As  the  wheel 
rolls — when  the  motion  is 
parallel  to  the  tracer-bar 
—and  as  the  shaft  slides 
under  the  roller-bearings 
without  friction  for  all 
movements  at  right  an- 
gles to  the  tracer-bar, 
there  is  no  scraping  on  the 
paper,  so  that  the  line 


FIG.  158. — Positions  of  the  planimeter. 


may  be  traced  without  varying  resistance,  and  the  personal  error 
due  to  the  operator  is  materially  reduced. 


THE   INDICATOR  AND   ITS  WORK  199 

WATER     USED     PER     HORSE-POWER     HOUR 

The  indicator-card,  besides  giving  the  horse-power  at  which  the 
engine  was  working  when  the  card  was  taken,  and  the  adjustments 
of  valves,  also  indicates  how  much  water  the  engine  is  using  per  hour. 
This  amount  is  usually  then  reduced  to  the  amount  of  water  required 
by  the  engine  per  horse-power  per  hour,  so  that  it  .can  be  compared  to 
other  engines,  as  each  engine  runs  under  varying  conditions  and  may 
be  of  a  different  type.  This  unit  is  taken  as  a  standard  of  comparison. 

The  indicator-card  assumes  that  all  the  steam  within  the  cylinder 
is  steam,  and  takes  no  account  of  initial  condensation  or  condensation 
during  expansion.  It  also  does  not  take  into  account  any  leakage, 
either  through  the  valves  or  past  the  piston.  The  only  way  that 
the  actual  amount  of  water  that  an  engine  uses  can  be  obtained  is 
by  direct  measurement.  This  is  done  either  by  condensing  the  steam 
after  it  has  passed  through  the  cylinder,  and  weighing  it,  or  by  weigh- 
ing the  water  before  it  enters  the  boilers  on  its  way  to  the  engine. 
However,  indicator-cards  must  be  taken,  from  which  the  horse- 
power is  obtained,  and  as  the  amount  of  water  that  the  engine  uses 
in  one  hour  can  be  measured,  by  dividing  that  quantity  by  the  horse- 
power the  real  amount  of  water  that  the  engine  uses  per  horse-power 
per  hour  can  be  obtained.  This  is  usually  a  very  laborious  and 
painstaking  process,  and  the  necessary  appliances  and  apparatus  are 
rarely  at  the  disposal  of  the  engineer. 

It  is  for  this  reason  that  the  indicator-cards  are  used  for  this 
purpose,  giving  as  they  do  an  indication  of  the  amount  of  water 
used  by  the  engine,  and  therefore  the  economy.  An  engine  always 
uses  more  water  than  that  represented  by  the  indicator-diagram, 
but  never  uses  less  water  than  that  shown  by  the  diagram,  so  that 
if  the  diagram  shows  an  uneconomical  consumption,  the  engine  is 
sure  to  be  uneconomical;  but  if  the  indicator-card  shows  that  it  is 
economical,  it  may  or  may  not  be  true.  This  latter  condition  depends 
upon  whether  there  is  much  initial  condensation  or  much  leakage. 
The  more  leakage  and  initial  condensation,  the  more  will  the  theo- 
retical amount  differ  from  the  actual  amount.  There  are  always 
some  leakage  and  initial  condensation  present  in  every  engine,  and  it 
is  for  this  reason  that  an  indicator-card  represents  the  least  amount  of 
water  that  the  engine  can  use. 


200  THE  INDICATOR  AND  ITS  WORK 

The  method  for  finding  this  amount  is  explained  as  follows:  The 
clearance-space  of  the  engine  should  be  known.  By  clearance  in 
this  case  is  not  meant  the  mechanical  clearance  between  the  head  of 
the  cylinder  and  the  piston  when  the  latter  is  at  the  end  of  the 
stroke,  but  the  volume  of  steam  that  is  required  to  fill  the  valve- 
passages  plus  this  mechanical  clearance. 

The  data  that  should  be  known  about  the  card  are  its  length,  the 
scale  of  the  indicator-spring  with  which  it  was  drawn,  and  the  horse- 
power, which  can  be  obtained  from  the  area  of  the  card  by  the  usual 
formula  : 

PLAN 


where  P  =  mean  effective  pressure  in  square  inches  ;  A  =  area  of  cylinder 
in  square  inches;  L  =  length  of  stroke  in  feet;  N  =  number  of  strokes 
per  minute.  , 

The  mean  effective  pressure  is  obtained  by  multiplying  the  area 
of  the  card  by  the  scale  of  the  spring  and  dividing  the  product  by 
the  length  of  the  card; 

-r,    area  of   the  card  .         ,      ,  ,  u 
or,  P  =  —  —  r  X  scale  of  the  spring. 

length  of  the  card 

The  most  accurate  method  of  procedure  is  to  assume  some  point 
on  the  expansion-line  of  the  card,  as  at  A  (Fig.  159),  and  find  the 
pressure  that  corresponds  to  it.  The  line  Am  represents  the  position 
of  the  piston  at  the  point  A.  As  no  more  steam  can  enter  the  cylinder 
from  the  boiler  after  cut-off,  any  point  can  be  taken  on  the  expansion- 
curve  after  cut-off.  The  percentage  of  clearance  being  known,  the  line 
OG  is  erected  at  a  distance  from  the  admission-line  equal  to  that 
percentage  of  the  length  of  the  card.  That  is,  if  the  clearance  is  3^ 
per  cent.,  the  distance  C  is  3^-  per  cent,  of  the  distance  L.  Next  find 
the  pressure  of  the  steam  at  point  A.  This  is  obtained  by  measuring 
the  height  Am,  and  multiplying  it  by  the  scale  of  the  spring. 

Assuming  for  the  diagram  an  initial  gauge-pressure  of  145  pounds, 
card  =  4.08  inches  in  length,  exhausting  on  or  near  the  atmospheric  line; 

x  =  .75  inch,  and  j—  -  =  .183  cut-off.  Gauge-pressure  at  A  =  120  pounds; 

gauge-pressure  at  B,  60  pounds;  and  the  mean  effective  pressure  is 
found,  as  before  described,  to  be  41  pounds  per  square  inch.  Then 


THE  INDICATOR  AND   ITS  WORK 


201 


for  1  cubic  foot  of  steam  in  the  cylinder,  the  weight  at  120  pounds 
gauge  by  the  steam-table  is  .304  pound.     As  the  proportion  of  a  cubic 

foot  contained  in  the  rectangle  xA.m  is    —  =  .  183  per  cent.  of  a  cubic 


I*  1  nr\   t  -«  r\r\  r\  f  f  /->r»  1  1    .UOOOO  X  OU  X  OO.UUU  1  o    /»  f  f* 

foot,  then  .304  X  .  183  =  .05563  pound,  and  -     —  —  —-^    -  =  18.656 

41.  X  -L44: 

60  X  33  000 
pounds  per  horse-power  hour.     Also  :  --  —  j  --  —  13,750,  a  constant, 


and 


.05563X13,750 
41 


=  18.656  pounds  per  horse-power  hour,  as  before. 


Then  for  any  size  cylinder  under  these  conditions,  its  volume  in 
cubic  feet  multiplied  by  the  speed  of  the  piston  in  feet  per  minute — 
by  60  and  by  .05563 — will  equal  the  total  weight  of  steam  consumed 
per  hour. 

For  the  additional  steam  required  to  fill  the  clearance  between 
the  volume  due  to  compression  and  that  due  to  the  initial  pressure, 


Vacuum  Line^ 


FIG.  159. — The  trial  indicator-diagram. 

we  find  for  145  pounds  initial  .pressure  .356  pound  per  cubic  foot,  and 
for  60  pounds,  .175.  Then  .356  -  .175  =  .181 X. 035  (clearance)  = 
.0063  + 18.656  =  18.662  pounds,  the  total  weight  of  steam  required  per 
horse-power  hour.  With  compressions  running  nearly  up  to  the  initial 
pressure,  the  differential  loss  is  of  inconsiderable  value;  but  with  no 
compression  the  loss  would  be  .356 X. 035  =  .01246,  or,  say,  1J  per  cent. 


202 


THE   INDICATOR  AND  ITS  WORK 


With  considerable  compression,  and  with  the  exhaust-line  above  the 
atmospheric  line,  as  shown  in  the  diagram,  the  computed  compression 
may  be  largely  increased  and  carried  up  to  the  initial  pressure;  and, 
inversely,  when  the  exhaust-line  is  below  the  atmospheric  line,  the 
assumed  compression  is  lessened. 

An  indicator-card  from  an  automatic  slide-valve  engine,  with 
cut-off  .115,  and  exhausting  at  2\  pounds  back  pressure,  is  shown  in 
Fig.  160.  This  engine  had  a  12  by  18  inch  cylinder;  revolutions,  124; 
boiler-pressure,  68  pounds;  initial  engine  pressure,  65  pounds;  corn- 


Spring  50 

Boiler  Press.  68  Lbs 
M.E.P.  25.5 


FIG.  160.  —  High-compression  card. 

pression,  57  pounds;  estimated  mean  effective  pressure,  25.5  pounds; 
computed  horse-power,  32.5.  Neglecting  the  clearance,  which  is 
nearly  compensated  by  the  excessive  compression,  and  including  the 
loss  by  the  steam  wasted  in  the  back  pressure,  we  find  the  pressure 
at  A,  from  the  atmospheric  line,  32  pounds,  at  which  pressure  1  cubic 
foot  of  steam  weighs  .113  pound. 


Then  £  = 


=  .3093  X.I  13  =  .03495  pound,  the  weight  of  steam 


used  per    cubic   foot   of   cylinder-volume,   and,  using   the   formula, 

W  13,750 

-rr-^p  —  p-  =  pounds  per  horse-power  hour. 

.03495X13,750  ,     ,  , 

Hence  -  —  —  —    —  =  18.8  pounds  of  steam  per  horse-power  hour. 
.25.5 

Then  for  the  total  steam-consumption,  18.8X32.5  =  611  pounds 
per  hour.     With  a  loss  of  15  per  cent,  by  condensation  during  ad- 

18  8 

mission,  then  -~  ==22.1  pounds  per  horse-power  hour,  or  a  total  of 
0.85 

718  pounds  per  hour. 


THE  INDICATOR  AND  ITS  WORK 


203 


INDICATOR-KINKS     AND     ADMISSION     AND 
TERM INAL      LINES 

The  distortions  of  the  lines  of  the  indicator-card  are  frequently 
made  a  cause  of  inquiry  by  engineers,  and  for  their  better  understand- 
ing we  illustrate  some  of  these  kinks,  with  their  accounting. 

Fig.  161  is  a  fairly  good  card  showing  a  small  advance  of  the  cut- 
off at  the  head-end  over  that  at  the  crank-end,  which  also  shows  its 
effect  on  the  exhaust-end  by  the  fuller  curve.  The  cut-off  of  .37  at 
the  head-end  and  .34  at  the  crank-end  shows  this  effect.  It  is  not  the 
most  economical  power-card,  as  the  exhaust  commences  at  40  pounds 
and  would  make  a  better  showing  of  steam-economy  at  one-fourth  to 
three-tenths  cut-off;  but  with  an  automatic  cut-off  these  are  neces- 


Rcv.  280 

Boiler  Press.  110 
Spring  60 


FIG.  161. — Automatic  cut-off  card. 


sarily  variable  points.  The  compression  is  one-half  the  initial  pres- 
sure, or  64  pounds,  which  should  make  a  smooth-running  engine  at 
the  speed  shown  on  the  card. 

The  wavy  expansion-lines  often  shown  on  indicator-cards  are 
mainly  due  to  friction  in  indicator  parts,  such  as  a  sticky  or  too  tight 
piston,  looseness  or  tightness  of  the  joints,  too  much  pressure  of  the 
pencil  upon  the  paper,  rough  paper,  irregular  tension  of  the  barrel- 
spring  by  touching  the  sides  of  its  chamber,  elasticity  or  vibration 
of  the  cord,  and  the  momentum  of  the  moving  parts — the  last  of 
which  is  greatly  increased  with  high  speed.  All  these  produce  irregu- 


204 


THE  INDICATOR  AND  ITS   WORK 


larities  not  due  to  valve-motion,  but  may  sometimes  become  accen- 
tuated by  leaky  valves. 

The   admission-   and   release-lines  as  shown   on  indicator-cards, 


FIG.  162. — Wavy  expansion-lines. 

have  distinct  bearings  on  the  action  of  the  indicator,   the  valves, 
and  the  steam  in  the  cylinder. 

The  diagram  A  Fig.  163  shows  that  at  the  moment  when  the  com- 
pression-line C  is  completed  the  valve  opens  quickly  and  throws  the 
admission-line  vertically  to  the  initial  pressure.  This  involves  the 
question  of  lead,  the  amount  of  which  the  size  of  the  engine  and  the 
speed  may  determine.  Lead  should  be  as  little  as  possible  and  allow 


\ 


FIG.  163. — Compression-  and  admission-lines. 


the  admission  to  be  vertical.  When  lead  is  made  to  admit  steam 
just  before  the  end  of  the  stroke,  the  compression-line  is  carried  up- 
ward, as  at  B.  This  has  been  a  matter  of  discussion;  but  the  con- 
sensus of  opinion  is  that  compression  should  be  high  with  small  lead, 
especially  with  high-speed  engines.  D  and  E  show  that  the  valves 
opened  late — so  much  so  in  E  as  to  invalidate  the  value  of  the  card 
for  economy. 

The  point  X  above  the  admission-line  Y  in  the  diagram   F  may 


THE  INDICATOR  AND    ITS  WORK 


205 


indicate  too  quick  opening  by  lead  and  the  momentum  of  the  moving 
parts  of  the  indicator  from  the  sudden  pressure — more  often  made  by 
high-speed  engines. 

The  steam-lines,  Fig.  164,  indicate  variations  in  the  normal  action 
of  valves,  in  which  G  shows  a  full  opening  to  the  boiler-pressure  dur- 
ing admission,  H  a  too  small  steam-pipe  or  excessive  speed,  I 


FIG.  164. — Steam-lines. 

probably  a  large  steam-chest  and  small  steam-pipe,  and  J  a  light 
load  and  early  cut-off.  K  shows  slight  compression  and  steam  ad- 
mission just  past  the  centre — a  good  indication  for  a  pounding  engine. 

The  line  L  in  Fig.  165  has  the  compression-line  rising  to  the  point  C 
and  forming  a  small  loop,  caused  by  late  admission,  the  valve  not 
opening  until  the  return-stroke  is  well  under  way. 

The  diagram  M  shows  a  still  later  opening  of  the  valve  sometimes 
met  with,  in  which  the  loop  may  vary  in  size  and  be  carried  to  the 


FIG.  165. — Erratic  admission-lines. 


top  of  the  card,  as  in  the  diagram  N,  when  the  compression-line  extends 
above  the  steam-pressure  in  high-speed  engines  from  over-compres- 
sion and  late  valve-opening.  The  same  effect  is  shown  in  diagram  0 
for  light  load  and  short  cut-off.  An  offset  in  the  compression-line, 


206 


THE   INDICATOR  AND   ITS  WORK 


as  0  at  P,  indicates  a  leak  during  compression  by  a  valve  lifting 
from  its  seat — generally  the  exhaust-valve  in  four-valve  engines. 

The  diagram  Q  Fig.  166  shows  that  the  exhaust  closes  too  late 
to  cause  any  compression,  the  piston  starting  on  its  return  just  be- 
fore the  inlet-valve  opens,  when  steam  may 
blow  through  the  exhaust- valve. 

In  the  diagram  R  the  exhaust-valve  does 
not  close  until  the  piston  is  well  on  its  way, 
causing  a  slight  vacuum  before  the  inlet- 
valve  opens,  owing  to  slipping  of  the  eccen- 
tric, thereby  making  the  whole  valve-motion 
late. 

The  forms  of  the  release-lines  are  relative 
counterparts  of  the  steam-  and  admission- 
lines,  and  are  subject  to  abnormal  proportions  depending  upon  the 
steam-lines  and  the  exhaust-valve  action. 

In  the  diagram  B  Fig.  167  the  dropping  of  the  expansion-line 
below  the  exhaust  is  very  undesirable  in  a  working  engine,  except 
in  extreme  conditions  of  load  or  in  friction  trials.  The  loop  B  varies 


FIG.  166. — Faulty  valve- 
setting. 


FIG.  167. — Release-lines. 

in  form  and  length  by  the  action  of  the  exhaust-valve.  In  the  diagram 
C  the  release  takes  place  at  D  by  too  early  opening  and  throttling 
of  the  exhaust-valve,  whereas  the  opening  should  be  made  at  E,  as 
shown  by  the  dotted  line,  and  a  small  saving  made  in  the  mean 
effective  pressure.  A  better  release  is  shown  at  F  and  H.  There  can 
be  no  object  in  delaying  the  release  causing  increase  of  pressure  at  the 
moment  of  exhaust,  as  shown  at  G  and  J,  the  latter  being  a  late  release 
on  a  condensing-engine,  of  which  K  is  a  good  example  of  a  slow  release. 
The  small  drop  near  the  end  of  the  expansion-line  generally  shows  a 


THE  INDICATOR  AND  ITS  WORK 


207 


slow  action  of  the  exhaust-valve,  or  a  throttling  in  the  exhaust- 
passages. 

In  Fig.  168  are  shown  two  sets  of  cards  from  a  high-pressure 
cylinder — 30x48 — at  87  revolutions  per  minute,  exhausting  into  a 


RECEIVER  PRESS.  25  LBS. 


PRESS  103  LBS. 

1- ^ 

RECEIVER  PRESS.  25  LBS. 


FIG.  168. — Exhaust-lines. 

receiver  under  a  varying  load.  The  sweeping  upward  of  the  exhaust- 
line  through  the  middle  of  the  stroke  shows  a  throttling  of  the  exhaust- 
passages  between  the  high-pressure  cylinder  and  the  receiver. 

Much  more  might  be  written  in  regard  to  the  eccentricities  ob- 
served on  indicator  cards,  due  to  the  combined  effects  of  valve-gear 
setting  and  its  looseness  of  joints;  irregularities  of  indicator  move- 
ments and  transmission  devices;  but  we  think  enough  has  been 
shown  to  cover  the  leading  faults,  from  which  the  origin  of  minor 
irregularities  shown  on  cards  may  be  readily  located. 


CHAPTER    XIV 

STEAM-ENGINE   PROPORTIONS 

ECONOMY  in  the  use  of  steam  is  one  of  the  first  considerations  in 
the  design  of  a  steam-engine.  The  cylinder,  its  principal  part,  should 
have  its  relative  dimensions  of  diameter  and  stroke  as  nearly  equalized 
as  possible,  unless  other  requirements — such  as  speed,  or  lightness 
of  parts,  or  of  the  whole  engine — suitable  for  its  special  service,  may 
be  inducements  for  designing  the  longer  stroke  and  slower  speed,  as 
used  in  the  comparatively  slow-speed  Corliss  type.  A  large  propor- 
tion of  the  high-speed  engines  of  to-day  are  designed  on  the  short- 
stroke  ideal. 

The  considerations  for  the  condition  of  the  steam  are  essential, 
and  may  be  taken  as  follows: 

Saturated  steam  is  steam  of  the  temperature  due  to  its  pressure. 

Superheated  steam  is  steam  heated  to  a  temperature  above  that 
due  to  its  pressure. 

Dry  steam  is  steam  which  contains  no  moisture,  and  it  may  be 
either  saturated  or  superheated. 

Wet  steam  is  steam  containing  intermingled  moisture,  mist,  or 
spray,  with  a  temperature  equal  to  that  of  dry  saturated  steam  at 
the  same  pressure. 

The  following  formulas  for  steam-engine  proportions  are  quoted 
from  various  authorities,  and  show  slight  differences  derived,  probably, 
from  different  lines  of  investigation  and  experience  in  formulating 
values  for  steam-engine  design.  The  builders  of  to-day  may  have 
arrived  at  still  different  values  and  proportions  in  their  practice. 

INITIAL  CONDENSATION. 

Q<    /rn x\ 

Bodmer :  W  =  weight  of  steam  condensed = C  — §~=-    pounds  per 

minute.  L  y  JN 

T  =mean  admission-temperature; 
t  =mean  exhaust-temperature; 


STEAM-ENGINE  PROPORTIONS  209 

-  S  =  clearance-surf  ace  in  square  feet; 
N  =  number  of  revolutions  per  second; 
L  =  latent  heat  of  steam  at  mean  admission-temperature; 
C  =  constant  for  any  given  type  of  engine. 

For  high-pressure,  non-jacketed  engines,  C  =  about  .11;  for  con- 
densing, non-jacketed  engines,  C=  .085  to  .11;  for  condensing  jacketed 
engines,  C  =  .085  to  .053.  The  figures  for  jacketed  engines  apply  to 
those  jacketed  in  the  usual  way,  and  not  at  the  ends. 

C  varies  for  different  engines  of  the  same  class,  but  is  practically 
constant  for  any  given  engine. 

The  condensation  may  be,  under  varying  conditions,  from  20  to 
50  per  cent,  of  the  weight  of  steam  given  to  the  engine. 

THE  CYLINDER — DIAMETER. 

Bodmer:  P  =  mean  effective  pressure  in  pounds  per  square  inch; 
L   =  length  of  stroke  in  feet; 
A  =area  of  piston  in  square  inches; 
N  =  number  of  strokes  per  minute; 
r    =  ratio  of  length  of  stroke  in  inches  to  the  distance 

travelled  by  piston  in  inches  before  cut-off; 
pi  =  initial  pressure  in  pounds  per  square  inch; 
p2  =  absolute     boiler  -  pressure  =  gauge    reading  +  15 

pounds. 
If  pipe  from  boiler  is  well  lagged : 

pi  =yf  p2  (Whitham); 

-r,       1+hyp.  log.  r         ,      , 

-  pi  -back  pressure; 

I.  H.  P.  x 38,000 
PLN 


Diameter  =  D  =  2  A  /  A  =  205  A  /L  H"  R. 
V.  TT  V    PLN 


Thurston  gives  D  =  ^  L  to  L. 

For  compound  engines  design  the  low-pressure  cylinder  by  the 
same  formulas  used  in  designing  a  single-cylinder  engine,  for  the  total 
power,  given  initial  and  exhaust  pressures,  and  total  expansion.  The 
size  of  the  high-pressure  cylinder  is  then  determined  by  the  table  of 
cylinder-ratios. 


210 

CYLINDER-RATIOS 
Grashof : 

Hrabak : 
Werner : 
Rankine : 


STEAM-ENGINE  PROPORTIONS 
IN  COMPOUND  ENGINES. 


Busley: 

CYLINDER-RATIOS 
Whitham: 


V  =  volume  of  low-pressure  cylinder; 
v  =  volume  of  high-pressure  cylinder; 
r  =  ratio  of  expansion. 
fBoiler-pressure  in         j  ^        ^ 
J  pounds  per  square  inch  I 
V 


105 


120 


I 


4.5 


IN  TRIPLE-EXPANSION  ENGINES. 


VOLUMES,  HIGH  TO  Low. 


Boiler-pressure  gauge. 

High  pressure. 

Intermediate. 

Low  pressure. 

130 

140 
150 
160 

1 
1 
1 
1 

2.25 
2.4 
2.55 

2.7 

5 
5.85 
6.9 
7.25 

For  170  and  upward,  use  quadruple-expansion. 


Common  rule :  Ratio  of  volumes  of  high  to  intermediate,  and  that 


of  intermediate  to  low,  are  each  equal  to  y  r,  and  the  ratio  of  high 


to  low  =  V  r2. 

Seaton: 

VOLUMES,  H 

[GH  TO  LOW. 

Boiler-pressure, 
absolute. 

High. 

Intermediate. 

Low. 

125 

2 

5 

135 

2 

5.4 

145 

2 

5.8 

155 

2 

6.2 

165 

2 

6.6 

STEAM-ENGINE  PROPORTIONS  211 

General  practice: 

Diameter  of  intermediate  cylinder  =  1.5  diameter  of  high; 

Diameter  of  low-pressure  cylinder  =  2. 5  diameter  of  high. 
Length  (as  given  by  Whitham) : 

Length  of  bore  =  L  +  breadth  of  piston-ring  =  -|-  to  \  inch ; 

Length  between  heads  =  L  +  thickness  of  piston  +  sum  of  clear- 
ances at  both  ends. 

CYLINDER  THICKNESS. 

t  =  thickness  of  cylinder  in  inches. 
Thurston:  t  =  apiD  +  b: 

pi  =  initial   unbalanced   steam-pressure   in   pounds   per 

square  inch; 

a  is  a  constant,  equal    to    .0004    in    short-stroke    or 
vertical-cylinder  engines,  and  equal  to   .0005  in 
long-stroke  or  horizontal-cylinder  engines; 
b  is  a  constant  varying  from  0  to  ^  inch. 
Whitham :     t  =  .03  l/p  D  jfor  any  size  cylinder  ; 
t  =  .003  D  4/p  for  small  cylinders; 
p  =  boiler-pressure  in  pounds  per  square  inch. 
Seaton:        t  =  .5  +  .0004p  D. 
Unwin :         t  =  .02  D  +  .5  to  .05  D  +  .5  (variable) . 
Van  Buren:  t  =  .0001  D  p  +  .15  V  D. 
Weisbach :    t  =  .8  +  .00033  p  D. 
Haswell :       t  =  .0004  p  D  +  i  f or  vertical ; 

t  =  .0005  p  D  +  l  for  horizontal. 
Marks:          t  =  . 00028  p  D. 

Rankine :      t  =          ; 

f  =  tensile  strength  of  material,  with  a  factor  of  safety, 

from  30  to  40. 

Barr:  t  =  .05  D  +  .3  inch,  a  formula  which  represents  the 

average  practice  of  modern  engine-builders. 

CYLINDER-HEADS. 

Thurston :     t  =  .000333  D  p  +  .25  ; 

D  being  diameter  of  circle  in  which  the  thickness  is 

taken;  _ 
t  =  .005D4/p+.25. 


212 


STEAM-ENGINE  PROPORTIONS 


Marks:          t  =  .003D|/p; 

t  =  .  00035  pD. 
Seaton:         t  =  .0005  p  D  +  .25; 

t  =  .0022  p  D  +  .93. 
Kent  :  t  =  .00036  D  p  +  .31,  which  represents  average  practice. 

CYLINDER-HEAD  BOLTS. 

Whitham  :     Diameter  of  bolt-circle  =  D  +  twice  the  thickness  of  the 

cylinder  +  twice  the  diameter  of  bolts. 
Bolts  should  not  be  more  than  6  inches  apart. 


Marks : 


^'  5» 

d  =  diameter  of  bolts  at  root  of  thread; 
n  =  number  of  bolts. 


n  =  .  0001571 


c  =  area  of  one  bolt. 

Thurston:     Distance  between  bolts  =  four  to  live  times  thickness 
of  flanges; 


Barr: 


n  =  .7D; 
d  =  .025D  +  .5. 

Both  of  Barr's  formulas  represent  average  practice 
among  builders  of  modern  low-speed  engines. 


CYLINDER-FLANGES. 

Thurston:   Thickness  of  cylinder-flanges  is  usually  made  equal  to 

the  thickness  of  flanges  of  the  heads. 

Barr:  Thickness  of  flanges  =  1.2  times  the  thickness  of  the 

cylinder. 


CLEARANCE. 
Seaton  : 


to  f  inch  for  roughness  of  castings,  and  -fa  to  -J-  inch  for 
each  working-joint. 


STEAM-PIPE. 

Kent:  Pipe-diameter  =  .408 


STEAM-ENGINE  PROPORTIONS  213 

EXHAUST-PIPE. 

Area  =  25  to  50  per  cent,  greater  than  area  of  steam-pipe. 

VALVE-PORTS. 

Kent :  Length  of  port  =  .8  D ; 

ALN  .    , 

Area  of  steam-port  =  -———  in  teet; 
o,UUU 

Area  of  exhaust-port  =  1.5  area  of  steam-port. 

,  ALN 

Barr:  Area  of  steam-port  = , 

c 

where  c  =  5,500  in  high-speed  engines, 
and  c  =  6,800  in  low-speed  engines. 

STEAM-CHEST. 

Thurston:  Thickness  =  .003  D/p. 
Seaton:      Thickness  =  .7  (.25 +  .0005  p  D). 

Number  and  size  of  bolts  are  to  be  determined  as  for 
cinder-head. 

VALVE-STEM. 

Whitham :  Diameter = -^  D ; 

=-|  diameter  of  piston-rod. 

PISTON. 

Marks :        Thickness  of  piston-head  =  V  L  D. 
Barr:          Piston-face  =  .46  D  for  high-speed  engines; 
=  .32  D  for  low-speed  engines. 

Whitham:  Thickness  of  piston  =  breadth  of  ring  +  thickness  of 
flange  on  one  side  to  carry  the  ring  +  thickness  of 
follower-plate. 

PlSTON-RlNGS. 

Seaton :      w  =  .63  (.02  D  /p  +  1) . 
Whitham:  w  =  .15  D. 
Unwin:       w  =  .014  d  +  .08. 
Kent:          t  =  .0333  D  +  .125; 

w  =  width  of  ring  in  a  direction  parallel  to  the  axis  of 

the  cylinder; 
t  =  thickness  of  ring  on  a  radial  line. 


214  STEAM-ENGINE  PROPORTIONS 

ECCENTRIC  PISTON-RINGS. 

Maximum  thickness  =  .05  D ; 
Outside  diameter  of  ring  =  1.05  D; 
Inside  diameter  of  ring  =  .97  D; 
Eccentricity  of  inner  circle  =  .01  D; 
w  =  f  to  f  inch. 

Kent:  Mean  thickness  =  .0333  D  +  .125; 
Minimum  thickness  =  f  maximum. 

PlSTON-ROD. 

Unwin:  d"=b  D|/~]p; 

p  =  maximum  unbalanced  pressure  in  pounds  per  square 

inch; 

b  =.0167  for  iron  and  .0144  for  steel; 
d"  =  k  D/^ 

k  is  a  constant,  depending  on  the  stress  f,  allowed  in 
the  material  as  follows : 


f 

2,000 

2,500 

3,000 

3,500 

4,000 

k 

.0224 

.02 

.0182 

.0169 

.0158 

f  =3,000  to  3,600  in  short-stroke  direct-acting  engines: 
f  =2,000  to  2,500  in  long-stroke  horizontal  engines. 


Thurston:d"  = 


JpL2 


+  .0125D; 


a  =10,000  in  high-speed  engines  and  15,000  in  low- 
speed  engines. 

Marks :       d"  =  .0179  D  ^"p  for  iron  ; 
d"  =  .0105  D/p"for  steel. 

Seaton:      d"  =  -=-/p; 

F  =45  to  60  for  direct-acting  engines. 
Whitham:  d"=k  D; 

k  =.1  for  wrought  iron  on  condensing-engine ; 

=  .08  for  steel  on  condensing-engine; 

=  .125  for  wrought  iron  on  non-condensing  engine; 

=  .10  for  steel  on  non-condensing  engine. 


STEAM-ENGINE  PROPORTIONS 


215 


1  =  length  in  inches. 

L  =  inches. 


Kent:        d"  =  .013VD  1  p; 
Barr :          d"  =  .145 4/D  L  for  low-speed  engines; 
d//  =  .ll'/D  L   for  high-speed  engines. 

CROSS-HEAD  SLIDES. 

The  thrust  on  the  guide  when  the  connecting-rod 
is  at  its  maximum  angle  with  the  line  of  the 
piston-rod  =  P,  tangent  of  the  angle  Z,  whose  sine 
_  stroke  of  piston 

2  X  length  of  connecting-rod' 
P  =  .7854D2p; 

.          ,   r  ,      P  tangent  Z 
Area  of  slide  =  —  — : 

Po 

p0  =  allowable  pressure  per  square  inch  on  slide. 
Seaton:       p0<400  pounds  per  square  inch. 
Rankine:    p0  =  72.2  pounds  per  square  inch. 
Whitham :  p0  =  100  pounds  per  square  inch. 
Thurston:  p  V  <  60,000  and  >  40,000; 

V  =  relative  velocity  in  feet  per  minute  of  the  rubbing- 
surfaces. 

Barr:          Area  =  .63  A  for  high-speed  engines; 
=  .46  A  for  low-speed  engines. 

CROSS-HEAD  PIN.  * 

Q  -p    .  .7854  D2  p 

Seaton:  Projected  area  =  —  ? 

1,200 

o,      „         .        (  Length  =  1.4  diameter  of  piston-rod. 
Small  engines  <  _-.  .  0_  v  ,    .  .  , 

(  Diameter  =  1.25  diameter  01  piston-rod. 

Whitham  says  the  bearing-surface  is  found  by  the  formula 

for  crank-pin  design. 

Barr:       Projected  area  =  .08  A  for  high-speed  engines; 
=  .07  A  for  low-speed  engines. 

CONNECT!  NG-ROD. 

Ratio  of  length  of  connecting-rod  to  stroke: 
Thurston:    2  or  2J-  to  1. 
Whitham:    2  to  4J-. 
Marks:         2  to  4; 

d"  =  diameter  of  circular  connecting-rods  larger  at  the 
middle. 


216  STEAM-ENGINE  PROPORTIONS 


Whitham:    d"  (at  middle)  =  .0272  f  D  1  V  p; 

1  =  length  of  connecting-rod  in  inches; 
d"  (at  necks)  =  1  to  1.1  diameter  of  piston-rod; 
Diameter  at  the  crank-pin  end  =  1.08  times  the  diam- 
eter at  the  cross-head  end.     The  rod  is  larger  at 
the  middle  and  tapers  about  -|  inch  to  the  foot. 
Marks :         d"  =  .0179  D  4/  p,  if  diameter  is  greater  than  -fa  length ; 

d"  =  . 02758  4/D  1  4/l^if  the  diameter  found  by  the 
previous  formula  is  less  than  -^  length. 

Thurston:    d"  (at  middle)  =  a  V  D  L  V  p  +  C; 

a  =  .15  and  C  =  .5  for  fast  engines; 

a  =  .08  and  C  =  .75  for  moderate  speeds. 
Donaldson:  d"  (at  necks)  =  .0024  D2  p. 

Sennett:       d"  (at  middle)  =  .01818  D  /~p~; 
d"  (at  necks)  =  .01666  D  /p!" 

Seaton :        d"  =  .02758  4/J)  1  V~p. 
Kent:          d"  =  .021  Dj/jT 
Barr:  d"  =  .092  4/1)1 

RECTANGULAR  CONNECTING-ROD. 


Thurston:  t  =  .0209  V  D  1  |/  p  +.47; 

t  =  distance  between  parallel  sides; 

Depth  at  cross-head  end  =  1.5  t; 

Depth  at  crank-end  =  2. 25  t. 
Kent:         t  =  .01  D  /~p~+  .6. 

BOLTS  IN  END  OF  CONNECTING-ROD. 
Whitham :  Diameter  at  root  of  thread 
D 


for  Steel; 


_  length  of  connecting-rod  e 

length  of  crank 
p=  maximum  pressure. 


STEAM-ENGINE  PROPORTIONS  217 

CAP  ON  END  OF  CONNECTING-ROD. 
Whitham :  Depth  of  cap  at  centre 


J    n  D2  p 

T   r 


=2-7  l  V  t.™,/TT— r  for  rigidity; 


Depth  of  cap  at  centre  =  1.5  D  4/  --  -  ; 

1  =  length  of  cap  between  bolt-centres; 
b  =  breadth  of  cap; 

E  =  modulus  of  elasticity  of  metal  used: 
=  28  million  for  wrought  iron, 
42  million  for  steel,  and 
18  million  for  cast  iron; 
b  =\  to  \  length  of  journal  =  diameter  of  neck  of  con- 

necting-rod +  \  to  \  inch; 
d  =  depth   of  cap  =  .6    diameter  of    connecting-rod  =  .8 

diameter  of  bolts  +  pitch  of  thj"ead  on  bolt. 
CRANK-PIN. 

Marks  :         1  =  .0000247  f  p1  N  D2  =  1.038  f  L  H>  P>. 

L 

Whitham:    1  =  .9075  f 


L 

1=  length  of  crank-pin  journal  in  inches; 
p1=mean  pressure  in  cylinder  in  pounds  per  square 

inch; 
f  =  coefficient  of  friction,  from  .03  to  .05  for  perfect 

lubrication,  and  from  .08  to  .1  for  imperfect  lubri- 

cation. 

Thurston:  1=ljo?ooforsteelpins;  •        "'      . 

P  N    ,      . 
1  =60^000  forlr°npms; 

PV 


60,000  d' 

V  =  velocity  of  rubbing-surface  in  feet  per  minute; 
P  =  mean  total  load  on  pin; 
d  =  diameter  of  pin. 


218 


TJ     v-          i 

Rankme:  !  == 


STEAM-ENGINE  PROPORTIONS 

P  (V  +  20) 


Unwin 


Unwin 


1      pod' 

P  =  greatest  load  on  pin; 

Po  =  pressure  in  pounds  per  square  inch  of  bearing; 
po  varies  from  150  to  200  in  small  land  engines,  and 
from  400  to  800  in  large  land  and  marine  engines; 
1_aI.H.  P.. 

r  =  crank-radius  in  inches; 
a  =  .3  to  .4  for  iron  pins; 
a  =  .066  to  .1  for  steel  pins. 

4 


d  = 


HVF; 

po  f 


f  =  twisting-stress,  say  5,000  pounds  per  square  inch. 

3    /CC  1   ~p  1 

Thurston:  d  =  A/    '         for  wrought  iron;  increase  d  10  per  cent. 
r     y,uuu 

in  case  of  steel; 
P=  maximum  load  on  the  piston. 

Unwin  :       d  =  .0947  to  .0827  Y¥\  for  wrought  iron; 

T  for  steel. 


d  =  .0827  to  .0723 


Marks : 


4  4    /  TT     p    13 

d  =  .066  */P  I3  D2  =  .945  y  ""^  ; 

P  =  maximum   steam-pressure  in  pounds  per  square 
inch. 

J/2H.P.1 

V  -~LW~ ; 


Whitham:  d  =  .0827  V  P  1  =2.1058 


d  =  .4054/PR 

Barr:  Projected  area  =  a  =  .24  A  for  high-speed  engines; 

a  =  .09  A  for  low-speed  engines; 


1  =.3 


TT 


-'  +  2.5  for  high-speed  engines; 


TT      T> 

1  =  .6  — '- — '•  +  2  for  low-speed  engines. 


STEAM-ENGINE  PROPORTIONS  219 

CRANK. 

Thurston:  b  ^ -7854  f  D*  p  R  secant  z  1 

a  d2 

b  =  thickness  of  web 
d  =  width  of  web ; 
1  =  radius  of  crank; 
p  =  maximum    unbalanced    pressure    in    pounds   per 

square  inch; 

z  =  angle  of  rod  with  centre-line  of  the  engine; 
f  =  factor  of  safety. 

The  diameters  of  the  hubs  are  about  twice  the  diameters  of  the 
corresponding  shafts,  and  d,  at  either  end,  is  three-fourths  the  diameter 
of  the  adjacent  hub. 

Empirical  rules  adopted  by  builders  give  for  wrought  iron: 

Hub-diameter  =  1.75  to  1.8,  the  least  diameter  of  that 

part  of  the  shaft  carrying  full  load; 
Eye-diameter  =  2  to  2.25  times   the  diameter  of  the 

inserted  portion  of  the  pin; 
Hub-depth  =  1.0  to  1.2  diameter  of  shaft; 
Eye -depth  =  1.25  to  1.5  diameter  of  pin; 
Web-width  =  .7  to  .75  width  of  adjacent  hub  or  eye; 
Web-depth  =  .5  to  .6  depth  of  adjacent  hub  or  eye. 

Whitham:  Wx  =  f  k(2y)2; 
6 

k  =  thickness  parallel  to  shaft,  and  generally  =  .75  shaft- 
diameter  ; 

2  y  =  variable  width; 
x  =  distance  from  crank-pin  centre  to  place  where  2  y 

is  measured; 
f  =  allowable  stress  per  square  inch  of  material; 


W  =  .7854  D2p  , 

length  of  connecting-rod 

where  n  =  —  s- •  — . 

length  of  crank 

For  a  two-cylinder  engine  W  =  1.414,  and  for  a  three-cylinder 
engine  W  =  2  times  the  above  value. 


220  STEAM-ENGINE  PROPORTIONS 

SHAFT. 

When  designed  for  combined  twisting  and  bending: 

Whitham:  d 


T  =  greatest  twisting-moment  on  shaft  due  to  load  on 

the  piston; 
M  =  greatest   bending-moment   on   shaft   due  to  load 

on  the  piston;  _ 

T'  =  Equivalent   twisting-moment  =  M  +  4/  M2  +  T2   on 

outer  journal  for  overhung  crank; 

M      /~M2 
T  =  y  V  -J-  +  T2  for  double,  crank  arm. 

The  above  formula  gives  safe  values  except  with  very  heavy  fly- 
wheels, where  the  shaft  must  be  designed  with  reference  to  bending 
due  to  the  weight  of  fly-wheel  and  shaft. 
Kent:  d  =  .43  D  for  long-stroke  engines; 
d  =  .4  D  for  short-stroke  engines. 
For  two  cranky  at  90  degrees  : 
"" 


d-  1.832  |; 

T  =  maximum  twisting-moment  produced  by  one  piston; 
f  =  safe-  working  shearing-strength  of  material. 

LENGTH  OF  SHAFT-BEARINGS. 
Marks  :    1  =  .0000247  f  p  N  D2  ; 

f  =  coefficient  of  friction; 

p  =  mean  pressure  in  pounds  per  square  inch  on  piston. 

TT     .       ,     A  H.  P. 
Unwin:    1  =  -  ; 

r  =  radius  of  crank  in  inches; 
1  =  (.002  N  +  1)  d  for  wrought  iron; 
1  =  (.0025  N  +  1.25)  d  for  steel. 
Barr:       1  =2.2  d  for  high-speed  engines; 
1  =  1.9  d  for  low-speed  engines. 
FLY-WHEELS. 

DI  =  diameter  in  feet.=   '      . 

N 

Thurston:  Di=4L;  . 

W=  weight  =  1,000,000   —  —  ^  for  automatic  valve- 


STEAM-ENGINE   PROPORTIONS 


221 


gear  engines  and  ordinary  forms  of  non-condensing 
engines  with  a  ratio  of  expansion  from  3  to  5; 
p  =  mean  steam-pressure  in  pounds  per  square  inch; 

aAL 


W_ 


N2 


a  ranges  from  40  to  60  million,  with  an  average  value  of 
48  million. 


Rankine:    W  =  1,900,000 


V  =  variation  of  speed  per  cent,  of  mean  speed. 
Stanwood:  W  =  2,800,000  j^J^; 

D=  diameter  of  cylinder; 
S  =  stroke  in  inches. 

FLY-WHEEL  RIMS. 


'     N2    ' 

FLY-WHEEL  ARMS. 

WL 


Torrey :     b  = 


30 


W  =  load  in  pounds  acting  on  one  arm; 

L  =  length  of  arm  in  feet; 

S  =  strain  on  belt  in  pounds  per  inch  of  width,  taken  at 

56  for  single  and  112  for  double  belts; 
y  =  width  of  belt  in  inches; 
d  =  depth  of  arm  at  hub  in  inches  =  major  axis; 
b  =  breadth  of  arm  at  hub  in  inches  =  minor  axis. 
In  using  the  formula  assume  depth. 
Depth  and  breadth  can  be  reduced  by  about  J  at  rim. 


Unwin:     d  =  .6337 


=  .798 


-1  for  single  belts; 


for  double  belts; 


b  =  .4d; 

B  =  breadth  of  rim. 


222  STEAM-ENGINE  PROPORTIONS 

MAXIMUM  SPEED  OF  FLY-WHEELS. 

1 

80  feet  per  second  =  4,800  feet  per  minute;  R.  P.  M.-^ 


88  feet  per  second  =  5,280  feet  per  minute;  R.  P.  M.  = 


1,680 


D 


100  feet  per  second  =  6,000  feet  per  minute;  R.  P.  M.  =  — 
MAXIMUM  DIAMETER  IN  FEET  OF  FLY-WHEELS. 


80  feet  per  second  =  4,800  feet  per  minute;  D 


1,527 

R.  P.  M: 

1,680 


88  feet  per  second  =  5,280  feet  per  minute;  D  =      'r~    . 

100  feet  per  second  =  6,000  feet  per  minute;  D=    ^^  . 

R.  P .  M. 

D  =  diameter  of  wheel  in  feet. 

The  following  tables  of  the  principal  dimensions  of  high-  and  low- 
pressure  cylinders  have  been  compiled  by  Mr.  L.  L.  Willard,  a  designer 
of  Corliss  engines,  and  although  they  may  not  conform  to  the  practice 
of  every  builder,  may  be  a  good  schedule  of  reference  for  the  various 
sizes  of  cylinders  for  the  high  and  low  pressures  of  150  and  50  pounds 
respectively. 

TABLE  XXX. — HIGH-PRESSURE  CYLINDER-DIMENSIONS  FOR  150  POUNDS  STEAM- 
PRESSURE. 


i 

£ 

Counterbore. 

Thickness  of 

C 

1  Thickness  of 
steam-chest 

rt 

Thickness  of 
exhaust-chest 

"rt 

Diameter  of 
valves. 

Valve-bearing. 

C 

r 

Thickness  of 
solid  piston. 

Thickness  of 
bull-ring 
piston. 

Diameter  of 
steam-pipe. 

Diameter  of 
exhaust-pipe. 

Drilling-circle. 

Number  of 
studs. 

Diameter  of 

1 

Diameter  of 
foundation- 

A 

B 

C 

D 

E 

F 

G 

H 

I 

J 

K 

L 

M 

N 

0 

P 

12 

12] 

1 

1 

i 

\ 

Si 

24 

51 

4 

5* 

5 

6 

15 

10 

i 

! 

li 

14 
16 

14} 

16; 

1 

lj 

1 
1} 

I 

4 
4| 

2J 

2* 

61 

5| 

4 
4 

5* 

5* 

5 
6 

6 

7 

17 

19 

10 
12 

1 
1 

1! 

18 

18- 

1- 

i 

i 

5 

3 

6 

5 

6* 

7 

8 

21 

14 

1- 

20 

20; 

li 

i 

5 

3 

6 

5 

6^ 

8 

9 

23 

16 

1^ 

1,1 

22 

22, 

lj 

lj 

6 

34 

7i 

5* 

74 

9 

10 

25? 

18 

11 

24 

24} 

If 

lj 

6 

34 

8£ 

5* 

84 

10 

12 

18 

ii 

26 

26< 

li 

li 

'•  '• 

3* 

8* 

8* 

10 

12 

29 

20 

1^ 

28 

28} 

1} 

1} 

7 

3J 

10 

7 

10 

11 

13 

31f 

20 

if 

30 

30} 

li 

li 

74 

4 

10 

7 

10 

12 

14 

34 

24 

1 

2 

32 

32i 

1 

i; 

8 

4 

10 

7 

11 

12 

14 

36 

24 

1 

1 

2 

34 

34i 

r 

IJi 

' 

8* 

4 

114 

8 

12 

14 

16 

38 

28 

1 

2 

36 

36} 

lj 

. 

H 

!• 

\ 

9 

44 

124 

8 

12 

14 

16 

40 

32 

! 

f 

2 

STEAM-ENGINE   PROPORTIONS 


223 


TABLE  XXXI. — LOW-PRESSURE   CYLINDER-DIMENSIONS   FOR   50  POUNDS  STEAM- 
PRESSURE. 


1 

Counterbore.  1 

1  Thickness  of 
barrel. 

Thickness  of 
steam-chest 
wall. 

1  *  Thickness  of  1 
exhaust-chest 

i 

Diameter  of 
valves. 

1 

> 

-3 

Depth  of  cylin- 
der-head. 

Thickness  of 
solid  piston. 

Thickness  of 
bull-ring 
piston. 

r  Diameter  of 
steam-pipe. 

1  Diameter  of 
exhaust-pipe. 

1 
Q 

Number  of 
studs. 

Diameter  of 

1 
n 

Diameter  of 
foundation- 

A 

B 

C 

D 

E 

F 

G 

H 

I 

J 

K 

-L 

M 

N 

0 

P 

20 

20J 

If 

1 

' 

: 

5 

3 

6 

6 

64 

7 

8 

23 

16 

r 

14 

22 

22^ 

H 

1 

- 

• 

6 

34 

74 

6 

64 

8 

9 

25f 

18 

r 

1^ 

24 

24J 

If 

1 

1 

r 

6 

34 

84 

6 

8 

9 

10 

27x 

18 

1 

li 

26 

26^ 

If 

li 

64 

34 

84 

6 

8 

9 

10 

29 

20 

1 

\- 

28 

28^ 

If 

H 

1 

7 

3f 

10 

7 

9 

10 

12 

31f 

20 

1 

l\ 

30 

3QJ 

: 

14 

H 

1 

74 

4 

10 

7 

10 

10 

12 

34 

22 

1 

2 

32 

32J 

: 

14 

If 

1 

8 

4 

10 

8 

12 

12 

14 

36 

22 

li 

r 

2 

34 

34^ 

- 

14 

if 

1 

84 

4 

10 

8 

12 

12 

14 

38 

24 

1 

2 

36 

36^ 

if 

if 

1: 

9 

44 

12 

84 

14 

14 

16 

40 

26 

li 

r 

2 

38 

38: 

' 

if 

if 

9 

44 

12 

84 

14 

14 

16 

42 

28 

1- 

2 

40 

40 

if 

14 

9 

44 

12 

84 

15 

16 

18 

44 

28 

1- 

2 

42 

42 

if 

14 

10 

5 

13 

9 

15 

16 

18 

46 

28 

1- 

2 

44 

44: 

if 

14 

1 

10 

5 

13 

9 

15 

16 

18 

48 

32 

li 

2: 

46 

46: 

if 

14 

• 

10 

5 

14 

94 

164 

18 

20 

50 

32 

li 

2J 

48 

48^ 

if 

14 

. 

11 

6 

14 

104 

164 

18 

20 

52 

32 

li 

2i 

50 

50^ 

if 

1 

11 

6 

15 

104 

174 

20 

22 

54 

36 

li 

2t 

52 

52^ 

11 

if 

1 

12 

7 

15 

104 

174 

20 

22 

56 

36 

lj 

\ 

54 

54^ 

11 

if 

l! 

12 

7 

15 

11 

18 

20 

22 

58 

36 

li 

. 

56 

56^ 

2 

if 

l\ 

12 

7 

16 

12 

18 

20 

22 

60 

36 

1 

- 

23 

58 

58i 

2 

if 

I] 

12 

7 

16 

12 

20 

22 

24 

62 

40 

1 

- 

60 

604 

2 

if 

12 

7 

16 

12 

20 

22 

24 

64 

40 

li 

- 

1\ 

The  piston  of  a  steam-engine  has  been  a  matter  of  much  study 
with  engine-designers  in  order  to  counteract  the  wear  of  both  piston 
and  cylinder  from  excessive  frictional  action.  The  early  form  of  a 
solid  bearing-surface  drifted 
into  the  form  of  a  solid  pis- 
ton with  one  or  more  plain 
and  eccentric  snap  -  rings 
with  followers,  which  later 
developed  into  a  composite 
piston  of  almost  as  many 


FIG.  169. — Composite  piston. 


variations  as  there  are  build- 
ers of  engines,  for  almost 
every  designer  has  a  kink  of  his  own,  which  he  always  regards  as  the 
best.  In  Fig.  169  is  shown  a  composite  piston,  consisting  of  a  spider 
and  a  follower-plate  that  clamps  a  bull-ring,  which  is  made  adjustable 


224 


STEAM-ENGINE  PROPORTIONS 


FIG.  170. — Segmental  piston. 


by  lock-screws  for  keeping  the  piston-rod  concentric  with  the  cylinder; 
the  lock-screws  are  threaded  in  the  web  of  the  spider,  with  lock-nuts 
on  the  inside.  On  the  left  side  of  the  cut  is  shown  the  single-snap 
spring-ring  held  out  by  flat  springs  against  shoulders,  and  at  the  right 

a  double  spring  with  the  same  con- 
struction. This  piston  is  used  on  the 
engines  of  the  Murray  Iron  Works 
Company. 

Another  model,  Fig.  170,  has  a 
packing-ring  made  in  six  segments, 
with  halved  joints,  and  set  out  against 
the  cylinder- walls  by  small  coil-springs 
held  in  brass  sockets  screwed  into  the  bull-ring.  The  bull-ring  is 
adjusted  by  lock-screws  in  the  web  of  the  spider. 

In  Fig.  171  are  represented  the  cross-head  and  a  half-section  of  the 
piston  as  made  by  the  Hewes  &  Phillips  Co. 

The  cross-head  is  secured  to  the  piston-rod  by  a  thread  and  nut, 
or  a  taper  fit  with  a  cross-key  which  draws  the  rod  firmly  to  the  shoul- 
der. The  wedge  form  of  a  gib  at  the  top  and  bottom  of  the  cross-head 
provides  means  for  adjustment. 

The  sliding  surfaces  of  the  gibs  are  faced  with  antifriction  metal, 
and  the  surfaces  of  these  gibs  are  amply  large  for  the  severest  duty. 

The  design  of  the 
cross-head  is  such  as 
to  entirely  avoid  the 
springing  of  the  piston- 
rod  or  any  tendency 
to  force  the  cross-head 
out  of  line. 

The  piston  is  a 
strongly  ribbed  cast- 
ing, securely  fastened 
to  the  piston-rod  by 

forcing.     It  is  further     FIQ  17L_Hewes  &  Phmips  cross.head  and  piston. 
secured  by  a  strong  and 

substantial  key  midway  in  its  bearing  in  the  piston.  The  end  of  the 
rod  is  also  riveted.  There  is  a  tendency  in  all  pistons  to  wear  down 
or  get  out  of  centre.  When  this  occurs  the  piston-rod  is  liable  to  be 


STEAM-ENGINE  PROPORTIONS 


225 


grooved  and  the  gibs  of  the  cross-head  to  wear  unequally  on  their 
opposite  ends.  To  obviate  this  the  piston  is  furnished  with  a  solid 
bull-ring,  against  which  suitable  screws  with  jam-nuts  are  provided 
for  adjustment.  By  this  means  perfect  alignment  of  the  piston  with 
the  cylinder  can  be  readily  secured. 

The  bull-ring  is  a- solid  casting  turned  in  such  a  manner  as  to  have 
a  full  semicircular  bearing  on  the  lower  half  of  the  cylinder.  At 
either  end  of  the  bull-ring  are  narrow  piston-rings,  which  wipe  over 


FIG.  172. — Harris  piston. 

the  counterbore  at  each  end  of  the  cylinder,  so  that  no  shoulders 
can  be  worn  on  its  surface. 

In  this  design  of  piston  the  packing  is  self-acting  in  its  adjustment, 
while  the  adjustment  for  alignment  can  be  readily  made  by  removing 
the  follower  and  setting  up  the  screws  provided  for  this  purpose. 

In  Fig.  172  are  shown  a  plan  and  section  of  the  Harris  piston,  con- 
sisting of  a  seven-part  spider  and  as  many  locked  set-screws  for  central 
adjustment.  The  rings  are  also  in  seven  spliced  segments,  set  out 
with  helical  springs. 

As  the  piston,  together  with  the  piston-packing,  is  one  of  the 
most  important  parts  of  the  engine,  particular  attention  has  been 
given  to  its  design  and  construction. 

It  is  forced  upon  the  rod  by  hydraulic  pressure,  which  in  the 


226 


STEAM-ENGINE  PROPORTIONS 


*s 


FIG.  173. — Nordberg  cross-head. 


larger  sizes  the  bearing  is  made  the  full  thickness  of  the  piston,  with  a 
steel  collar  screwed  on  the  end  of  the  rod;  otherwise  a  recessed  nut, 
as  shown. 

The  bull-ring  extends  over  the  full  width  of  the  piston,  overlapping 
the  piston  and  the  follower.  It  is  grooved  to  receive  the  segmental 
packing. 

All  of  the  Harris  pistons  are  fitted  with  bronze  adjusting-screws, 
so  that  they  can  be  kept  centrally  within  the  cylinder  and  that  the  rod 

may  always  be  in  perfect  alignment. 

In  Fig.  173  is  shown  a  cross-head 
of  the  Nordberg  engine,  which  is  ad- 
justed by  a  top  and  bottom  wedge 
\\    |  jj      and  screws  with  lock-nuts.     The  ad- 

l_4_^=4 -IPIA  \~--y   J II      justment  of  the  cross-head  for  keeping 

the  piston-rod  in  the  central  line  and 
parallel  with  the  piston-bore  is  an 
essential  part  of  engine-management; 
and  these  designs  are  most  numerous, 
but  all  having  or  seeking  the  required 
ideal  of  perfect  control  and  fixedness  of  the  adjustment. 

In  Fig.  174  is  shown  a  similar  arrangement  in  the  cross-head  of 
the  Murray  engine,  with  cylindrical  Babbitted  bearings  on  wedge- 
shoes  that  are  bolted  to  the 
main  block. 

The  design  of  the  connect- 
ing-rods  and  the  method  of 
adjustment  of  their  boxes 
vary  very  much  with  engine- 
builders,  the  wedge  and  screw 
being  in  general  use. 

In  Fig.  175  is  shown  the 
rod-end  used  by  the  W.  A. 
Harris  Company,  in  which  the 

inner  box  has  an  inclined  back  with  a  wedge  and  draw-screws  on  each 
side.  The  screw  sprevent  a  possible  movement  of  the  wedge  by  the 
motion  of  the  rod. 

In  Fig.  176  is  shown  the  connecting-rod  end  of  the  Filer  &  Stowell 
Co.,  on  which  the  ad  justing- wedge  is  placed  horizontally  at  both  ends 


FIG.  174. — Cylindrical  cross-head. 


STEAM-ENGINE  PROPORTIONS 


227 


of  the  rod,  and  adjusted  by  a  collar-bolt  and  lock-nuts.     A  set-screw 
underneath  is  added  as  a  safety-check. 

The  main  bearings  of  a  steam-engine  require  the  same  care  as  its 
other  running  parts — not  only  in  providing  for  its  proper  lubrication, 
but  also  as  the  means  for  taking 
up  of  the  boxes  to  meet  the  wear. 


FIG.  175. — Cross-key  box. 


FIG.  176. — Side-key  box. 


In  horizontal  engines  the  thrust  of  the  piston  may  cause  a  pound  in 
the  main  bearing  by  looseness  from  wear,  and  in  vertical  engines  the 
wear  in  the  journal-boxes  is  vertical  from  the  action  of  the  piston, 
but  may  also  be  crosswise  from  the  belt-pull. 


FIG.  177. — Main  bearing,  Bayley  engine. 

In  Fig.  177  are  shown  a  half-view  and  half-section  of  the  self- 
lubricating  main  bearing  of  the  Bayley  engine,  in  which  a  ring  dips 
into  the  oil-chamber  below,  and,  rolling  over  the  top  of  the  journal, 
gives  it  a  constant  and  economical  oil-feed.  A  gauge-glass  connected 


228 


STEAM-ENGINE  PROPORTIONS 


to  the  bottom  of  the  chamber  shows  the  height  of  the  oil,  and  the 
drip-cock  allows  of  drawing  off  the  oil  and  cleaning  the  chamber 
when  required. 

The  adjustable  main  bearing  used  on  the  Todd  engine  is  shown  in 
section  in  Fig.  178,  in  which  the  quarter-boxes  on  each  side  are  ad- 


FIG.  178. — Main  bearing,  Todd  engine. 

justed  by  wedges  at  their  back  and  by  long  stud-bolts  reaching  through 
the  cap  with  locking-nuts.  The  cap  of  this  bearing  has  a  hand-hole 
and  cover  large  enough  to  allow  the  journal-surface  to  be  examined 
while  the  engine  is  running. 

THE     FLY-WHEEL 

The  most  important  element  in  controlling  the  motion  of  a  steam- 
engine  is  that  which  equalizes  its  transmission  of  speed.  The  fly- 
wheel takes  action  before  the  governor  in  all  motors  or  engines  that 
receive  their  impulse  in  unequal  increments,  and  the  more  unequal 
the  impulse  the  more  important  is  the  office  of  the  fly-wheel. 

Its  power  to  equalize  the  speed  of  revolution  depends  upon  its 
weight  and  rim-velocity,  while  the  governor  only  regulates  the  im- 
pellent force  that  drives  the  engine.  Solid  fly-wheels  of  cast  iron  as 
ordinarily  made  are  limited  to  a  rim-speed  of  about  one  mile  per  minute, 
with  their  usual  diameter  limited  at  8  feet,  and  from  8  to  16  feet  in 
halves,  divided  through  the  arms  or  between  them.  Above  16  feet 
in  diameter  sectional  wheels  are  of  the  usual  construction,  with  the 
joints  at  the  end  of  the  arms,  and  sometimes  with  the  arm  and 
section  cast  in  one  piece. 


STEAM-ENGINE  PROPORTIONS 


229 


Fig.  179  shows  a  channel  rim- wheel,  as  usual  made  in  halves,  and 
Fig.  180  a  heavy  rim-wheel  in  sections  bolted  to  the  arms. 

The  ultimate  strength-efficiency  of  the  wheel  divided  in  halves, 
with  ordinary  bolting  at  hub  and  rim,  is  about  25  per  cent.,  the  sec- 


FIG.  179. — Wheel  in  halves. 


FIG.  180. — Sectional  wheel. 


tional  about  50  per  cent.,  and  with  heavy  rim-wheels  reenforced  with 
links  shrunk  on,  an  efficiency  of  60  per  cent,  may  be  obtained. 

In  the  following  table  are  given  the  number  of  revolutions  of  solid 
wheels  and  the  different  models  of  sectional  wheels  according  to  their 
percentage  of  efficiency,  with  a  speed-margin  of  safety  of  one-third 
of  their  tensile  strength. 

This  table  has  been  computed  on  the  assumption  of  100  feet  per 
second  rim-speed  as  the  maximum  safe  velocity  of  the  rims  of  solid 
cast-iron  wheels. 

For  sectional  wheels  with  flange-joints  between  the  arms, 
100X4/.25  =  50  feet  per  second. 

For  sectional  and  belt  wheels  having  joints  at  the  end  of  the  arms 
and  rim-sections,  100  X  V  •  50  =  70 . 7  feet  per  second. 

For  thick-rimmed  sectional  wheels  having  rim-joints  reenforced 
by  steel  links  shrunk  on,  100  X  V  •  60  =  77 . 5  feet  per  second. 

From  this  may  be  deduced  the  number  of  revolutions  for  any 
diameter  of  the  four  conditions  of  efficiency:  For  solid  wheels,  1,910  H- 
diameter  in  feet;  for  sectional  belt- wheels  and  split  wheels  with 
joints  between  the  arms,  955  -=-  diameter  in  feet;  for  sectional  belt- 
wheels  with  additional  joints  at  end  of  arms,  1,350-=-  diameter  in 
feet;  for  thick-rimmed  sectional  wheels  having  rim-joints  reenforced 
by  steel  links  shrunk  on,  1,480  -*-  diameter  in  feet. 

The  weight  and  diameter  of  a  fly-wheel  are  matters  of  much  con- 
sideration in  their  design  to  meet  the  most  economical  conditions  of 
the  variable  forces  due  to  impulse,  local  limitations,  and  weight  of 
metal  to  satisfy  the  requirement. 


230  STEAM-ENGINE  PROPORTIONS 

TABLE  XXXII. — SAFE  SPEED  FOR  CAST-IRON  FLY-WHEELS. 

EFFICIENCY  OF  RiM-JoiNT. 


1.00 

.25 

.50 

.60 

Diameter  in  feet. 

R.  P.  M. 

R.  P.  M. 

R.  P.  M. 

R.P.M. 

1 

1.910 

955 

1,350 

1,480 

2 

955 

478 

675 

740 

3 

637 

318 

450 

493 

4 

478 

239 

338 

370 

5 

382 

191 

270 

296 

6 

318 

159 

225 

247 

7 

273 

136 

193 

212 

8 

239 

119 

169 

185 

9 

212 

106 

150 

164 

10 

191 

96 

135 

148 

11 

174 

87 

123 

135 

12 

159 

80 

113 

124 

13 

147 

73 

104 

114 

14 

136 

68 

96 

106 

15 

128 

64 

90 

99 

16 

120 

60 

84 

92 

17 

112 

56 

79 

87 

18 

106 

53 

75 

82 

19 

100 

50 

71 

78 

20 

95 

48 

68 

74 

21 

91 

46 

65 

70 

22 

87 

44 

62 

67 

23 

84 

42 

59 

64 

24 

80 

40 

56 

62 

25 

76 

38 

54 

59 

26 

74 

37 

52 

57 

27 

71 

35 

50 

55 

28 

68 

34 

48 

53 

29 

66 

33 

47 

51 

30 

64 

32 

45 

49 

For  automatic  valve-geared  engines  we  quote  Professor  Thurston's 
general  rule  as  the  means  of  practice  to  meet  the  special  conditions 
of  engine-running: 

Weight  of  fly-wheel  =250,000          ^ ,  in  which  A  =  area  of  piston 

-L\>      JL/ 

in   square    inches;    S  =  stroke  in  feet;    p  =  mean  effective    pressure; 
R  =  revolutions  per  minute;  D  =  outside  diameter  of  fly-wheel  in  feet. 


STEAM-ENGINE   PROPORTIONS  231 

As  rim-velocity  increases  as  the  diameter,  and  as  centrifugal  force 
increases  as  the  square  of  the  rim-velocity,  the  centrifugal  force  must 
bear  a  safe  proportion  to  the  minimum  tensile  strength  of  the  rim 
for  assigning  the  weight  and  diameter  of  a  fly-wheel  for  any  assumed 
speed. 

The  total  strain  in  a  fly-wheel  rim  by  centrifugal  force  is  :  , 

g  R 
in  which  W  =  the  total  weight  of  the  rim  in  pounds;  V2  =  the  square 

of  the  velocity  of  the  rim;  g  =  the  gravity  32.  16,  and  R  =  the  radius  of 
the  wheel  in  feet. 

For  example:  a  wheel-rim  1  inch  square  and  12  inches  outside 
diameter  would  have  a  mean  diameter  of  1  1  inches  X  3  .  14  =  34  .  54 
cubic  inches;  at  .25  pounds  per  cubic  inch  =  8.  64  pounds.  At  a 
speed  of  1,910  revolutions  per  minute,  1,910x3.1416  =  6,000  feet  per 


minute,  or  100  feet  per  second.     Then  =  5,360  pounds, 

32  .  lo  X  .  5  it. 

the  total  strain  due  to  centrifugal  force;  and  as  there  are  two  sides 


Pv 

to  the  rim  on  which  this  force  is  divided,  then    '      >  =  2,680  pounds 

strain  per  square  inch,  or  about  one-half  the  elastic  limit  and  one- 
fourth  of  the  lowest  tensile  strength  of  cast  iron. 


THE     CONNECTING-ROD     ANGLE 

The  position  of  the  piston  in  parts  of  its  stroke  does  not  coincide 
with  its  position  in  parts  of  the  crank-rotation,  as  will  be  seen  by 
comparing  the  scales  A  and  B,  Fig.  181,  made  from  the  angular  posi- 
tions of  a  connecting-rod  of  twice  the  stroke  in  length.  The  upper 
scale,  A,  is  in  equal  parts  of  the  piston-stroke,  while  the  lower  scale,  B, 


FIG.  181. — Piston-  and  crank-stroke. 


232  STEAM-ENGINE  PROPORTIONS 

represents  the  corresponding  scale  for  equal  increments  of  the  crank- 
pin  half-circle  for  one  stroke.  It  may  be  noted  by  the  scale  that  at 
the  half-stroke  of  the  crank  the  piston  has  advanced  about  f  of  JQ-  of 
its  stroke,  and  that  in  the  return-stroke  the  advance  will  be  the  same, 
making  1}  of  y^-  of  its  stroke  difference  in  the  positions  of  the  piston 
during  a  revolution.  The  displacement  of  the  position  of  the  piston 
at  half-crank  stroke  may  be  readily  computed — say,  for  a  10-inch 
stroke  and  20-inch  piston-rod — by  the  right-angle  equation,  as  follows : 
202-52  =  375,  and  1/375"=  19.365,  and  20  - 19.365  =  .625,  or  f  inch, 
or  a  difference  of  1^  inches  in  the  forward  and  back  stroke  of  the 
piston.  Short  eccentric-rods  produce  the  same  irregular  motion  of 
the  valve  in  a  small  degree  by  advancing  its  position  at  the  middle 
of  each  stroke. 

There  is  much  in  steam-engine  design  that  cannot  be  detailed  in 
a  general  treatise  as  shown  in  this  work. 

Experience  is  the  most  important  factor  in  the  details  of  construc- 
tion that  a  designer  should  have  in  order  to  accomplish  good  results 
from  the  theory  and  in  the  line  of  modern  practice. 

The  foregoing  chapter  is  characteristic  of  the  views  of  authors  on 
the  proportions  of  the  leading  parts  in  construction  design;  they 
may  vary  somewhat  from  the  most  recent  practice  of  builders,  but 
will  make  a  good  study  for  the  inquiring  engineer  and  the  student 
in  steam-engine  design. 


CHAPTER    XV 


THE    SLIDE-VALVE   AND   VALVE-GEAR 

THE  slide-valve  of  our  forefathers  was  the  so-called  D  valve,  with- 
out lap  or  lead,  which  has  long  since  been  relegated  as  a  memorial 
of  primitive  experience.  The  D  valve  and  its  congener,  the  piston- 
valve,  as  we  now  understand  them,  are  modelled  after  our  modern 
ideas  of  the  economy  derived  from  expansion,  compression,  and 
steam-lead.  For  this  purpose  they  are  designed  with  extensions  of 
their  faces  for  steam-  and  exhaust-lap,  and  operated  by  the  angular 
position  and  throw  of  the  eccentric  for  steam-  and  exhaust-lead;  all 
of  which  are  made  variable  to  meet  the  special  contingencies  of 
design  in  engine-economics.  . 

In  Fig.  182  we  illustrate  the  modern  type  of  the  D  valve  with 
steam-  and  exhaust-lap,  and  in  its  central  position. 

The  portion  a  is  the  "steam-lap"  or  "outside  lap,"  and  the  por- 
tion b  the  "exhaust-lap"  or  "inside  lap,"  and  in  order  to  open  either 
port  to  steam  or  exhaust,  it  is  necessary 
for  the  valve  to  travel  from  mid-position  a 
distance  equal  to  these  laps,  and  for  a  full 
port-opening  a  greater  distance  than  the 
amount  of  all  the  laps,  or  equal  to  the 
steam-lap  and  port  width. 

In  the  ordinary  type  of  plain  slide-valve 
engine  with  throttle-valve  the  cut-off  is  fixed,  and  there  is  no  adjust- 
ment for  speed  variation  except  through  a  governor  and  throttle- 
valve;  while  the  automatic  high-speed  engines  are  provided  with  fly- 
wheel governors  which  vary  the  throw  of  the  eccentric  and  the  cut-off. 

Since  the  valve-travel  depends  upon  the  lap  and  lead,  both  of 
which  are  frequently  adjustable  irrespective  of  the  eccentric,  the 
conditions  in  the  cylinder  also  depend  upon  these  quantities,  and 
when  the  latter  are  determined  the  eccentric  must  operate  the  valves 
so  as  to  produce  the  required  lead. 

The  operation  of  the  valve  is  determined  by  inspecting  or  meas- 

233 


FIG.  182.— D  valve. 


234  THE  SLIDE-VALVE  AND  VALVE-GEAR 

uring  its  movements,  the  eccentric  thus  far  having  no  direct  influence 
upon  the  result.  When  the  lap  and  lead  are  decided  upon,  the 
eccentric  is  turned  until  the  desired  lead  is  obtained,  which  is  meas- 
ured at  the  valve  and  not  at  the  eccentric.  As  the  lead  with  a  given 
lap  depends  more  or  less  upon  the  lap  and  upon  lost  motion  in  the 
gear,  it  is  evident  that  these  quantities  must  first  be  determined 
and  the  eccentric  moved  backward  or  forward  on  the  shaft  until 
the  desired  movement  of  the  valve  is  obtained. 

When  the  required  steam-distribution  has  thus  been  established 
the  eccentric  will  occupy  the  proper  position  for  producing  the  re- 
sults, and  it  will  be  seen  that  it  makes  absolutely  no  difference  to  the 
engineer  whether  the  eccentric  leads  the  crank  by  98  or  105  or  any 
other  number  of  degrees.  The  position  of  the  eccentric  in  cases  of 
valve-setting  and  gear-adjustment  takes  care  of  itself  by  its  move- 
ment to  meet  the  valve-adjustment. 

It  will  no  doubt  be  apparent  that  the  truly  important  point  to 
be  observed  is  the  effect  of  lap  and  lead  on  the  steam-distribution. 
When  these  have  been  properly  determined  and  the  movements  of 
the  valve  regulated  and  timed  to  produce  them,  the  eccentric  will 
be  found  to  be  located  at  precisely  the  proper  angle  with  reference  to 
the  crank. 

SIMPLE     SLIDE-VALVE     GEAR 

The  relative  position  and  motion  of  the  eccentric-rod  and  valve- 
rod  are  points  of  consideration  in  the  design  of 'a  plain  slide-valve 
engine. 

In  determining  the  position  of  the  eccentric  in  cases  where  a 
rocker-arm  intervenes  between  the  eccentric-  and  valve-rods,  con- 


FIG.  183. — Direct  gear  for  running  "over.'! 

sideration  must  be  given  the  point  at  which  the  rocker-arm  is  pivoted. 
If  the  rocker-arm  is  pivoted  so  that  the  valve-  and  eccentric-rods 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


235 


both  move  in  the  same  direction  at  the  same  time,  the  eccentric  is 
set  in  the  positions  shown  in  Figs.  183  and  184,  which  illustrate  re- 
spectively the  different  parts  of  the  gear  in  the  proper  relative  positions 
when  it  is  desired  to  have  the  engine  run  "over"  and  "under." 


\ 


FIG.  184. — Direct  gear  for  running  "under." 

When  the  rocker-arm  is  pivoted  so  that  the  valve-  and  eccentric- 
rods  move  in  opposite  directions,  then  the  eccentric  must  be  set  in 
the  positions  shown  in  Figs.  185  and  186,  which  are  directly  oppo- 
site to  the  positions  shown  in  Figs.  183  and  184.  Here,  too,  the 
illustrations  show  the  engine  set  to  run  "over"  and  "under." 


FIG.  185. — Indirect  gear  for  running  "over." 

The  eccentric-rod  may  be  said  to  be  indirect-acting,  for  with  the 
rocker-arm  pivoted  as  shown  in  the  diagram  the  eccentric-rod  has 
a,  movement  that  is  directly  opposite  to  that  of  the  valve-rod. 

This  will  be  made  plain  by  a  study  of  the  diagrams  shown. 


FIG.  186. — Indirect  gear  for  running  "under." 

Fig.  184  shows  the  correct  position  of  the  eccentric  when  the 
engine  is  to  run  "under"  and  when  the  particular  valve-gear  shown  in 
Fig.  183  is  used. 


236 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


In  the  diagrams,  0  represents  the  crank-shaft,  A  the  crank-pin, 
C  and  D  the  points  at  which  the  valve-  and  eccentric-rods  are  con- 
nected to  the  rocker-arm,  E  the  pivot  for  the  rocker-arm,  and  F  and 
G  the  necessary  joints  for  the  valve-stems  and  piston-rods. 

A  good  rule  to  bear  in  mind  when  setting  engine-valves  that 
are  operated  by  these  simple  types  of  valve-gear  is:  When  a  slide- 
valve  is  used  and  the  eccentric-  and  valve-rods  move  in  the  same 
direction,  set  the  eccentric  ahead  of  the  crank  and  make  the  angle 
between  them  90  degrees  plus  the  angle  of  advance. 

The  above  rule  holds  good  whether  the  engine  runs  "under"  or 
"over."  On  the  other  hand,  when  the  valve-  and  eccentric-rods 
move  in  opposite  directions,  the  eccentric  must  be  set  behind  the 
crank,  and  the  angle  between  them  will  be  90  degrees  minus  the 
angle  of  advance. 

The  proper  positions  of  the  valve  must  be  determined  at  the 
valve,  whether  the  position  of  the  eccentric  be  located  first  or  last; 
but  when  observing  the  valve  first,  no  attention  need  be  paid  to  the 
position  of  the  eccentric. 

Few  would  care  to  undertake  the  work  of  placing  the  centre  of 
the  eccentric  at  a  given  angle  to  the  centre  of  the  crank,  and  no 
matter  how  carefully  the  work  may  be  done,  an  inspection  of  the 
valve,  in  nine  cases  out  of  ten,  will  prove  the  time  and  labor  to  have 
been  expended  uselessly. 

The  length  of  the  port-opening  is  usually  equal  to  or  little  less 
than  the  cylinder  diameter.  The  width  of  the  bridge  should  be 
amply  sufficient  to  prevent  steam  leaking  past  the  seal  into  the  ex- 
haust-port or  to  prevent  the  over-travel 
uncovering  the  steam-  and  exhaust-ports 
at  the  same  time. 

In  order  that  the  exhaust-port  shall  at 
no  time  be  contracted  to  a  less  area  than 
that  of  the  steam-port,  its  width  should 
be  such  that  it  will  at  all  times  retain  an 

T-,  opening  under  the  valve  equal  to  the  area 

FIG.  187. — Middle  and  extreme       *• 

valve-positions.  P*  the  steam-port  at  least. 

In  Fig.  187  is  shown  a  good-propor- 
tioned D  slide-valve  at  middle  and  extreme  travels  with  the  ex- 
haust-port of  a  width  more  than  double  the  width  of  the  steam- 


THE  SLIDE-VALVE  AND  VALVE-GEAR  237 

port,  which  allows  of  excess  of  valve-travel  without  restricting  the 
exhaust-opening. 

Such  a  valve,  having  an  outside  lap  of  \  inch,  inside  lap  of  -§-  inch, 
over-travel  of  f  inch,  with  ports  and  bridges  1  inch  each,  will  have  a 
travel  of  i  +  i  +  f +  1X  2  =  4  inches. 

In  laying  out  a  valve  it  often  happens  that  in  order  to  have  the 
points  of  release  and  compression  occur  at  a  particular  period  the 
inside  or  exhaust  lap  becomes  zero,  or  else  leaves  the  exhaust-port 
slightly  open  at  mid-position.  This  port-opening  is  known  as  nega- 
tive lap,  and  it  is  a  common  occurrence  to  find  a  valve  possessing 
negative  lap  when  not  so  designed,  due  to  the  effect  of  the  rod-angu- 
larity which  was  neglected  in  the  valve-diagram.  This  only  occurs, 
however,  when  the  original  exhaust-lap  is  very  small,  so  that  the 
small  error  caused  by  the  angularity  of  the 
rod  neutralizes  the  shortage  in  exhaust-lap 
entirely. 

The  zero  and  negative  laps  are  shown  in 
Fig.  188,  in  which  a  is  the  point  of  opening 

of  the  exhaust,  and  b  the  point  of  CUt-off     FIG.  188. — Negative  inside  lap. 

for  the  exhaust. 

The  lead  to  be  given  to  a  valve  depends  largely  upon  the  style 
of  engine,  and  must  be  governed  entirely  by  experience.  It  may 
vary  from  0  up  to  and  even  above  f  inch.  Slow^running  engines 
require  less  lead  than  those  running  at  a  high  speed,  and  engines 
having  a  high  compression  require  less  than  those  without,  since 
the  clearance-space  is  filled  with  compressed  steam  whose  pressure  is 
nearly  equal  to  that  of  the  entering  live  steam.  In  locomotives  it 
varies  from  0  to  \  inch,  and  in  marine  practice  from  0  to  1^  inches. 
In  stationary  practice  the  values  may  vary  from  0  to  \  inch,  but 
seldom  more,  unless  in  very  high-speed  work.  The  angle  of  lead, 
wilich  is  the  angle  that  the  crank  makes  with  the  dead  points  at 
admission,  varies  between  0  and  8  degrees  in  stationary  practice, 
and  seldom  over  10  degrees  in  marine  practice. 

The  inside  lead,  or  what  would  be  called  the  exhaust-lead,  is 
often  greater.  It  is  provided  for  the  purpose  of  opening  the  exhaust- 
port  early.  Weisbach  gives  the  proportion  of  -fa  to  fa  of  the  valve- 
travel. 

The  outside  lap  may  vary  from  \  inch  to  l£  inches  in  locomotives, 


238 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


while  in  marine  engines  it  may  run  from  J  inch  to  3|-  inches.  The 
inside  lap  may  vary  from  a  negative  value  to  J  inch,  and  in  marine 
practice  will  often  run  as  high  as  l^  inches. 

The  eccentricity  will  vary  largely  with  the  style  of  engine  and 
valve-travel  desired,  but  it  should  be  no  greater  than  necessary, 
owing  to  the  wear  on  the  reciprocating  parts.  In  marine  engines 
it  may  vary  from  5  to  8  inches,  or  even  more  in  large  units. 

Changing  the  dimensions  of  any  part  of  the  valve  which  determines 
either  the  lap  or  lead,  or  changing  the  angular  advance,  alters  the 
steam-distribution.  The  accompanying  table  shows  at  a  glance  just 
what  particular  effect  each  change  has  upon  this  distribution: 

TABLE  XXXIII. — EFFECT  OF  CHANGING  OUTSIDE  LAP,  TRAVEL,  AND 

ANGULAR  ADVANCE.  Thurston. 


CHANGE. 

ADMISSION. 

EXPANSION. 

EXHAUST. 

COMPRESSION. 

Increase  of 
outside  lap. 

Begins  later. 
Ceases  sooner. 

Occurs  earlier. 
Continues  longer. 

Unchanged. 

Unchanged. 

Decrease  of 
outside  lap. 

Begins  earlier. 
Ceases  later. 

Begins  later. 
Period  shortened. 

Unchanged. 

Unchanged. 

Increase  of 
inside  lap. 

Unchanged. 

Begins  as  before. 
Continues  longer. 

Begins  later. 
Ceases  earlier. 

Begins  sooner. 
Continues  longer. 

Decrease  of 
inside  lap. 

Unchanged. 

Begins  as  before. 
Period  shortened. 

Begins  later. 
Ceases  earlier. 

Begins  later. 
Period  shortened. 

Increase  of 
travel. 

Begins  sooner. 
Ceases  later. 

Begins  later. 
Ceases  sooner. 

Begins  later. 
Ceases  later. 

Begins  later. 
Ends  sooner. 

Decrease  of 
travel. 

Begins  later. 
Ceases  earlier. 

Begins  earlier. 
Ceases  later. 

Begins  earlier. 
Ceases  earlier. 

Begins  earlier. 
Ceases  later. 

Increase  of 
angular  advance. 

Begins  earlier. 
Period  unchanged. 

Begins  sooner. 
Period  unchanged. 

Begins  earlier. 
Period  unchanged. 

Begins  earlier. 
Period  unchanged. 

Decrease  of 
angular  advance. 

Begins  later. 
Period  unchanged. 

Begins  later. 
Period  unchanged. 

Begins  later.             ,  Begins  later. 
Period  unchanged.     Period  unchanged  , 

EXCESSIVE     COMPRESSION 

The  compression  is  sometimes  represented  in  indicator-diagrams 
as  excessive;  with  plain  D  valves  its  relief  cannot  always  be  found  in 
the  valve-gear  adjustment.  A  method  of  changing  the  exhaust-lap 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


239 


has  been  proposed,  and  is  shown  in  Fig.  189.  It  consists  in  filing  off 
the  edge  of  the  lap  for  small  amounts,  and  for  a  further  change  filing 
half-round  grooves  across  the  edge  of  the  lap  and  the  port  at  opposite 
points.  This  method  of  reducing  compression  will  slightly  interfere 
with  the  expansion-line,  but  not  to  any  serious  extent. 


FIG.  189. — Changing  the  exhaust-lap. 


W///W//A 
FIG.  190. — Balanced  valve. 


The  modifications  of  the  D  valve  for  more  perfect  action  have 
developed  some  curious  yet  valuable  features  in  their  design. 

The  balanced  valve  is  now  largely  in  use,  and  one  of  its  forms  is 
shown  in  Fig.  190,  which  carries  in  the  back  a  ring  which  bears  against 
a  smooth  seat  on  the  valve-chest  cover  and  is  supported  by  springs. 
The  cavity  at  the  back  of  the  valve  may  be  open  to  a  condenser  or 
through  the  back  of  the  valve  to  the  exhaust. 

As  one  representative  of  the  double-admission  type,  the  Allen 
balanced  valve,  illustrated  in  Fig.  191,  has  a  broad,  double-ported 
steam-passage  through  the  body  and  a  relief-port  from  the  cavity  at 
its  back  to  the  exhaust-cavity.  The  ports  of  the  supplementary 
passage  are  so  located  as  to  take  steam  to  the  port  at  the  moment  of 


FIG.  191. — Allen  balanced  valve.  FIG.  192. — Double-ported  slide-valve. 

opening  of  the  lap-edge  of  the  valve,  from  the  simultaneous  opening 
of  the  supplementary  port  at  the  other  end.  This  passage  never  com- 
municates with  the  exhaust,  for  its  outlet  to  the  main  port  is  closed 
just  before  the  port  opens  for  release,  and  is  opened  just  after  the 
port  is  closed  for  the  exhaust.  Its  economy  lies  in  its  short  travel. 
The  double-ported  marine  slide-valve,  shown  in  Fig.  192,  is  another 


240 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


FIG.  193.— Balanced 
slide-valve. 


novelty  in  the  line  of  double  ports.     It  is  in  use  on  marine  engines 
on  the  intermediate  and  low-pressure  cylinders. 

The  valve  is  shown  in  its  middle  position,  in  which  all  the  ports 
are  opened  and  closed  alike  and  with  but  slight  cut-off.     The  short 
_^^^_____     travel  required  by  double  ports  makes  this  type 
of  valve  desirable  in  the  triple  and  quadruple 
engines. 

A  type  of  balanced  slide-valve  much  in  use 
is  shown  in  section  in  Fig.  193,  consisting  of  a 
ring  held  in  a  recess  at  the  back  of  the  valve  and 
pushed  against  the  steam-chest  cover  by  springs. 
The  details  of  its  construction  vary  somewhat  in  the  different  engines 
to  which  it  is  applied.    The  relief-press- 
ure varies  from  60  to  80  per  cent. 

In  Fig.  194  are  shown  the  face  and 
back  of  a  balanced  slide-valve  and  the 
steam-chest,  with  the  valve  in  posi- 
tion as  used  on  the  Skinner  high-speed 
engine. 

The  valve  has  80  per  cent,  of  its 
area  relieved  of  pressure  by  a  balance- 
ring  which  rides  against  the  steam- 
chest  cover.  This  ring  is  free  to  re- 
volve, and  changes  position  with  every 
stroke  of  the  valve,  preventing  any 
creasing  or  cutting  of  seat,  ring,  or 
cover.  Steam  packing-rings  prevent 
leakage  between  the  ring  and  the  hub  of  the  valve.  This  construction 
allows  a  large  port-area,  which  is  necessary  for  proper  steam-distribu- 
tion. Twenty  per  cent,  of  steam-pressure  is  sufficient  to  hold  the 
valve  in  steam-tight  contact  with  the  seat  and  to  take  up  the  wear. 
The  valve  is  free  to  lift  from  the  seat  in  case  water  enters  the  cylinder. 


FIG.  194. — Balanced  slide-valve, 
Skinner  model. 


SLIDE- VALVES     WITH     A     RIDING     COVER 

Of  this  type  of  slide-valve  there  are  many  designs,  with  both 
single  and  double  ports  so  arranged  as  to  facilitate  a  full  passage  of 
steam  with  the  shortest  travel  of  the  valve.  In  Fig.  195  is  shown 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


241 


a  section  of  the  cylinder  and  steam-chest  of  the  Ames  engine.  The 
valve  is  a  two-ported  plate,  one  at  each  end,  riding  under  a  partially 
balanced  pressure-plate,  with  recesses  to  allow  of  double-port  openings 
and  a  short  valve-travel.  The  supplementary  port-opening  is  over 
each  end  of  the  valve-plate,  as  shown.  This  type  is  representative 
of  a  large  number  of  engine  slide-valves  by  different  builders. 


FIG.  195. — Ames  slide-valve. 


FIG.  196. — Chandler  &  Taylor  double- 
ported  slide-valve. 


In  Fig.  196  is  shown  a  section  of  the  cylinder  and  steam-chest  of 
the  Chandler  &  Taylor  engine — a  high-speed  model  designed  with 
special  adaptation  for  direct  electric  generator-connection. 

The  valve-plate  is  two-ported  at  each  end,  a  feature  making  it 
possible  to  give  a  large  port-area  with  short  valve- travel.  This  class 
of  valves  is  so  balanced  and  free  to  lift  that  there  is  little  or  no 
danger  from  slight  excess  of  water  in  the  cylinder. 


THE      SLIDE-VALVE     WITH     INDEPENDENT 
CUT-OFF 

The  most  economical  use  of  steam  requires  an  earlier  cut-off  than 
can  be  obtained  from  the  single  D  valve  and  a  proper  adjustment  of 
the  exhaust-  and  compression-lines. 

In  order  to  obtain  the  short  cut-off  with  the  required  conditions 
of  exhaust  and  compression  in  the  slide-valve,  a  number  of  devices 
have  been  proposed  and  used  in  Europe  and  the  United  States. 
Among  such  are  the  Gonzenbach,  with  a  three-ported  solid  rider  in  a 
separate  steam-chest  at  the  back  of  the  regular  D  valve;  the  solid 
sliding  valve  on  the  back  of  the  main  valve,  as  designed  by  Breval, 


242 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


Polonceau,  Napier  &  Rankih,  Farcot,  Borsig,  A.  K.  Rider,  and  other 
models,  most  of  which  are  used  in  locomotive  service. 

The  Meyer  expansion-valve  has  proved  its  value  for  stationary 
service  by  its  continued  use  for  more  than  a  half-century.     In  this 

valve  the  riding  cut-off 
consists  of  two  blocks 
adjusted  for  any  re- 
quired  cut-off  by  right- 
and  left-handed  screws 
on  a  traversing  spindle, 
as  shown  in  Fig.  197. 
A,  A  are  the  cut-off 

blocks  adjusted  by  the  right  and  left  threads  on  the  spindle  B,  which 
extends  through  both  ends  of  the  steam-chest,  with  a  swivel  at  G,  a 
wheel,  H,  for  turning  the  spindle,  and  an  index  at  i  to  designate  the 
amount  of  cut-off;  S  is  the  half- travel  of  cut-off  valve.  At  the  right  is 
a  diagram  of  the  eccentrics  and  crank-pin.  The  lap  and  lead  of  the 
main  valve  are  not  effected  by  the  operation  or  adjustment  of  the 
cut-off  valve. 

A  novel  arrangement  of  balanced  valves  with  simultaneous  move- 
ment for  both  cylinders  of  a  compound  tandem  type,  as  used  on  the 


FIG.  197. — Meyer  expansion-valve. 


By-pass 
Valve 


FIG.  198. — Union  valves,  compound  tandem  engine. 

locomotives  of  the  Pittsburg  Locomotive  Works,  is  shown  in  Fig.  198. 
The  cylinders  have  a  sleeve  between  the  heads  which  carries  the 
piston-rod  without  packing. 


THE   SLIDE-VALVE  AND   VALVE-GEAR 


243 


FIG.  199. — Brownell  balanced 
slide-valve. 


The  valves  are  connected  by  a  rod  passing  through  a  pipe  between 
the  steam-chests  of  the  high-pressure  and  low-pressure  cylinders. 
The  high-pressure  valve  receives  steam  through  the  balance-plate, 
which  is  movable,  with  piston-rings  for 
perfect  closure.  In  ordinary  use  the  ex- 
haust-steam from  the  high-pressure  cylin- 
der passes  through  the  pipe  covering  the 
connecting-rod  to  the  steam-chest  of  the 
low-pressure  cylinder.  A  by-pass  valve 
and  side  port  allow  of  turning  high- 
pressure  steam  directly  to  the  low-pressure 
cylinder  when  needed  for  starting. 

In  Fig.  199  is  shown  a  section  of  the 
cylinder  and  balanced  valve  of  the  Brownell  engine.  The  valve  is 
of  the  box  type,  double-ported  for  both  steam  and  exhaust,  and 
practically  perfectly  balanced. 

The  steam-pressure  is  removed  from  the  back  by  means  of  a  balance- 
ring  which  bears  against  the  steam-chest 
cover.  A  coil-spring  serves  to  keep  the  ring 
against  the  chest-cover,  thus  taking  up  the 
wear  automatically  and  preventing  the  ring 
from  leaving  its  seat  and  causing  annoy- 
ance by  rattling.  This  class  of  balanced 
valves  is  in  use  on  the  Skinner,  Ball  & 
Wood,  Payne,  Erie,  and  other  high-speed 
engines. 

A  balanced  valve  of  the  Wilson  type  is 
shown  in  three  positions  in  Fig.  200.  The 
uppermost  figure  shows  the  opening  posi- 
tion of  the  double  port;  the  middle  figure, 
the  wide-open  position,  and  the  lowermost 
figure,  the  exhaust  position.  The  gridiron 
form  of  the  valve  shortens  the  valve-travel 
and  doubles  the  port-area.  The  exhaust- 
ports  are  also  double  in  the  action  of  this 
valve.  The  ported  balance-plate  rests  un- 
der an  adjusting-plate  bolted  to  the  steam-chest  cover,  which  makes 
the  valve  almost  frictionless* 


/ALVE  IN  OPENING  POSITION 


VALVE  IN  EXHAUST  OPENING  POSITION 

FIG.  200.— Wilson  slide-valve. 


244 


THE   SLIDE-VALVE   AND  VALVE-GEAR 


In  Fig.  201  is  shown  the  balanced  slide-valve  of  the  Bay  ley  vertical 
automatic  engine.  The  pressure-plate  is  free  from  the  steam-chest 
cover  and  pressed  against  the  valve  by  a  spring;  it  is  held  in  place 
by  adjustable  stays  against  the  ends  of  the  steam-chest  and  by  side- 
bars to  prevent  lateral  motion. 

The  oscillating  cylindrical  valve,  shown  in  Fig.  202,  is  still  much 
in  use  on  hoisting-engines  with  cam,  eccentric,  or  secondary  crank- 
motion.  It  seems  to  be  well  adapted  to  the  operation  of  hoist- 
ing and  other  small  engines  by  the  simplicity  and  direct  action 
of  its  gear.  Steam  enters  at  the  top  of  the  cylinder  at  S  and  passes 
around  the  cylinder  to  the  valve- 
chest  at  P,  P — a  means  for  keeping 
the  cylinder  clear  of  water  while 


FIG.  201. — Bayley  slide-valve. 


FIG.  202.— Oscillating  valve. 


the  hoist  is  waiting.  The  valve-arm  V  is  directly  connected  to  the 
crank-pin  arm  at  E.  These  valves  operate  on  the  same  principle  as 
the  plain  slide-valve,  with  from  five-eighths  to  three-quarters  cut-off 
for  light  work,  or  full  stroke  for  heavy,  slow  pull  and  two  cylinders. 

The  gridiron  or  multiported  valve  is  much  in  use  in  the  marine 
service  and  on  the  stationary  engines  of  the  Slater  Engine  Company, 
Mclntosh  &  Seymour,  the  American  &  British  Mfg.  Co.,  and  C.  H. 
Brown  &  Co. 

In  Fig.  203  is  shown  a  cross-section  of  the  cylinder  of  the  Mclntosh 
&  Seymour  engine,  with  the  valve-gear  of  the  steam,  exhaust,  and  cut- 
off valves.  The  four  valves,  steam  and  exhaust,  are  operated  froni 
a  rock-shaft  at  M,  which  in  turn  is  rocked  by  a  fixed  eccentric  through 
a  bell-crank  lever  connected  to  a  crank  on  the  rock-shaft.  The  os- 
cillating pin  P,  on  the  rock-shaft  wrist-plate  at  M,  operates  the  exhaust- 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


245 


FIG.  203. — Gridiron  valves  and  cut-off. 


valve  by  a  direct  link  and  cross-head,  c,  while  the  steam-valve  is  oper- 
ated from  the  pin  P'  through  the  link-rod  S  and  toggle-joint  me. 
The  riding  cut-off  valve  is  operated  from  a  second  rock-shaft  located 
at  A,  with  its  variable  motion  controlled  by  the  fly-wheel  governor, 
which  revolves  the 
eccentric  to  advance 
the  cut-off  valve.  The 
connection  between 
the  eccentric  and 
rock-shaft  is  a  bell- 
crank  lever  with  a 
slipper  -  link  bearing 
on  the  eccentric  from 
one  arm  and  a  link  to 
a  crank-pin  on  the 
rocker-shaft. 

The  connection  between  the  rocker-shaft  and  the  cut-off  valve  is 
shown  in  the  figure  at  the  right  by  a  rocker-arm  at  A,  linked  to  a 
bell-crank  rocker  pivoted  at  a,  so  arranged  that  the  cut-off  valve 
moves  in  the  opposite  direction  to  the  main  valve,  and  with  the  rapid 
closing  of  the  ports  giving  a  sharp  corner  on  a  card  at  the  end  of  the 
admission-line. 

In  Fig.  204  is  shown  an  enlarged  section  of  the  gridiron  valve  and 
riding  cut-off  grid  of  the  Mclntosh  &  Seymour  engine. 

In  Fig.  205  is  shown 
T  a  section  of  the  steam 

-         MAIM 

and  exhaust  gridiron 
valves  and  valve-gear 
of  the  Brown  engine, 
and  in  Fig.  206  the 
motion  -  gear  of  the 
exhaust  -  valve.  The 

vertically  operated  steam-valves  and  steam-chest  are  on  the  side  of 

the  cylinder,  while  the  exhaust-valves  are  horizontal  and  beneath  the 

cylinder. 

The  operation  of  these  valves  may  be  understood  from  the  cuts 

and  reference-letters. 

The  lifter  A,  which  is  connected  to  the  lower  arm  of  the  bell-crank 


FIG.  204. — Section  of  gridiron  valve  and  cut-off. 


246 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


lever  B,  has  just  engaged  the  latch  C,  which  is  journalled  on  a  pin  on  the 
guide  D.  When  the  long  arm  B  is  drawn  toward  the  crank-shaft  by 
the  eccentric,  the  lifter  A  is  raised,  which  carries  the  latch  and  guide  up 
with  it  and  causes  the  valves  to  open  the  ports.  This  upward  move- 
ment continues  until  the  outer  end  of  the  latch  engages  the  trip-lever 
E,  which  causes  the  latch  to  let  go  of  the  lifter,  when  the  valve  im- 
mediately descends,  dropping  by  its  own  weight,  and  being  cushioned 
by  the  dash-pot  directly  under  the  guide,  which  movement  closes  the 
ports  and  effects  the  cut-off,  which,  owing  to  the  short  travel  of  the 


FIG.  205. — Gridiron  valves,  Brown  engine.  FIG.  206. — Exhaust  valve-gear. 

valve,  is  very  sharp,  permitting  no  wire-drawing  of  the  steam.  The 
trip-lever  E  is  carried  by  the  auxiliary  shaft  G,  which  is  connected 
to  and  is  actuated  by  the  governor. 

The  exhaust-valve  mechanism  is  shown  in  Fig.  206,  which  repre- 
sents a  plan.  The  exhaust-valves  have  a  positive  connection  with  the 
sliding  bar  A,  and  hence  have  an  unvarying  travel. 

When  the  sliding  bar  A  is  moved  to  the  right  in  the  cut  by  the 
exhaust-eccentric,  the  longer  arm  C  of  the  exhaust-lever  is  moved 
inward,  while  the  shorter  arm  is  moved  outward,  which  opens  the 
exhaust-ports,  the  reverse  movement  taking  place  when  the  port  is 
closed. 


THE   SLIDE-VALVE   AND   VALVE-GEAR 


247 


THE  DIAGRAM  OF  THE  SLIDE-VALVE  FOR 
CUT-OFF 

The  lay-out  of  a  slide-valve  diagram  is  an  easy  matter  when  once 
we  consider  its  simple  intricacies.  Assuming  that  the  lap  is  required 
and  that  the  lead  is  prefixed  to  some  definite  amount  between  the 
usual  variation  from  •£%  to  T\  inch  or  more ;  the~  lead  in  any  case 
being  kept  as  small  as  possible  to  allow  the  admission-line  on  the 
indicator-diagram  to  be  vertical;  to  find  the  lap  and  lead. 

A  diagram  for  cutting  off  at  three-quarters  stroke  is  shown,  in  Pig. 
207,  on  a  scale  in  parts  of  the  engine-stroke,  say  for  12  inch,  as 
shown  in  the  diagram, 
for  12-inch  stroke. 

In  this  diagram  the 
connecting-rod  angle  is 
not  considered,  but 
should  be  allowed  for  in 
precise  work,  as  shown 
in  the  foregoing  chapter. 

On  the  12-inch  base- 
line of  the  semicircle 
ABB  measure  the  dis- 
tance of  the  piston  from 
A  equal  to  the  cut-off,  say  9  inches,  and  from  this  point  draw  a  verti- 
cal line  to  the  semicircle  at  K;  draw  the  line  from  the  centre  0  to  K, 
and  the  line  Mn,  at  a  distance  from  AB,  equal  to  the  lead,  say  -^ 
inch.  K  is  the  position  of  the  crank-pin  at  three-quarters  stroke. 

Next  find  the  centre  of  a  circle  on  the  semicircle  described  by  the 
centre  of  the  eccentric,  and  describe  the  circle  EFG,  with  its  circum- 
ference tangent  to  the  lines  Mn  and  OK,  as  at  F  and  G. 

The  radius  of  this  circle  will  be  the  required  lap  to  be  added  to 
the  valve  in  order  that  it  may  cut  off  at  three-quarters  of  the  stroke. 
The  amount  of  lap  to  be  added  for  this  point  of  cut-off  is  { f  inch. 

The  diagram  will  also  show  the  amount  the  port-opening  has  been 
decreased  after  adding  lap  to  the  valve.  With  0  as  a  centre  and  the 
compass-pen  open  to  a  length  equal  to  the  distance  OE,  describe  an 
arc  of  a  circle  that  will  be  tangent  to  the  lap-circle  at  E,  and  the 


FIG.  207. — Lap-  and  lead-diagram,  three-quarters 
cut-off. 


248 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


distance  OE  is  the  amount  the  port  will  be  opened  when  the  eccentric 
is  at  its  greatest  throw,  which  in  this  case  is  1TV  inches. 

By  adding  lap  to  the  valve  we  have  also  changed  the  position  of  the 

centre  of  the  eccentric. 
Instead  of  being  in 
a  position  of  90  de- 
grees ahead  of  the 
crank,  it  must  now  be 
moved  a  considerable 
distance  beyond  this 
point  and  equal  to  the 
distance  BP,  or  31  de- 
grees, or  121  degrees 
ahead  of  the  crank. 


FIG.  208. — Lap-  and  lead-diagram,  five-eighths  cut-off. 


In  Fig.  208  is  shown  a  diagram  for  five-eighths  cut-off,  with  lead  as 
before  and  lap  of  If^  inches,  as  shown,  the  port-opening  being  reduced 
to  yf-  inch  and  the  angle  of  advance  being  increased  to  41-rj-  degrees,, 
the  total  advance  be- 
ing 131^-  degrees. 

Fig.  209  shows  a 
diagram  by  which  any 
position  of  the  valve- 
gear  and  the  different 
positions  of  the  valve 
may  be  found  when 
some  of  the  other 
events  are  known. 
Suppose  we  know  the 
valve-travel,  the  lap, 
and  lead,  and  want  to 
know  what  the  cut-off 
and  angle  of  advance 
will  be.  With  the 


FIG.  209. — Universal  valve-diagram. 


point  0  as  a  centre, 

and  a  radius  equal  to 

the   length  of    the  crank,  describe  the  circle  ARB.     The  diagram 

should  be  drawn  to  some  scale,  say  3  or  6  inches  to  the  foot.     The 

diameter  AB  of  the  circle  will  represent  the  stroke  of  the  engine,. 


THE  SLIDE-VALVE  AND  VALVE-GEAR  249 

and  the  circle  itself  will  represent  the  path  of  the  centre  of  the 
crank-pin  for  one  revolution. 

Again,  using  0  as  a  centre  and  a  radius  OD,  equal  to  one-half 
travel  of  the  valve,  describe  the  semicircle  CFD.  The  diameter  CD 
will  represent  the  travel  of  the  valve. 

Above  and  parallel  to  the  line  AB  draw  the  line  MN,  a  distance 
from  AB  equal  to  the  known  lead. 

Draw  also  the  line  HJ  parallel  to  the  line  MN,  and  a  distance 
above  it  equal  to  the  known  lap. 

The  line  HJ  will  intersect  the  semicircle  CFD  at  I,  and  with  I 
as  a  centre  and  a  radius  equal  to  the  distance  IG,  which  is  the  re- 
quired lap,  describe  the  circle  FEG. 

From  the  centre  0  draw  a  diagonal  line  that  will  be  tangent  to 
this  circle  at  F  and  will  intersect  the  large  circle  at  K. 

Next  draw  the  diagonal  line  from  the  centre  0  and  through  I  of 
the  lap-circle,  and  intersect  the  large  circumference  at  P.  K  will  be 
the  position  of  the  crank-pin,  and  L  will  be  the  position  of  the  piston 
in  the  cylinder  when  the  steam  is  cut  off.  The  angle  BOP  will  be 
the  required  angle  of  advance. 

Take  another  case,  where  we  know  the  valve-travel,  the  angle  of 
advance,  and  the  cut-off,  and  we  want  to  know  the  amount  of  lap 
and  lead.  Lay  off  the  stroke  the  same  as  before,  and  draw  the  cir- 
cumference described  by  the  centre  of  the  crank-pin,  and  suppose  the 
piston  and  crank-pin  to  be  in  the  same  positions  as  before,  at  L  and 
K.  Draw  the  perpendicular  line  LK,  and  from  the  centre  0  draw 
the  line  OK.  From  B  lay  off  the  angle  of  advance,  BOP.  The  line 
OP  will  intersect  the  semicircle  at  I.  With  I  as  a  centre,  draw  a 
circle  that  will  be  tangent  to  the  line  OK,  as  at  F.  Draw  the  line 
MN,  tangent  to  the  circle  just  described  and  parallel  to  the  line 
AB,  and  the  distance  between  the  lines  AB  and  MN  is  the  required 
lead,  and  the  radius  IG  will  be  the  required  lap. 

Take  another  case,  where  we  know  the  lap  and  lead  and  point 
of  cut-off,  and  wish  to  find  the  valve- travel  and  angle  of  advance. 
Proceed  the  same  as  in  the  previous  cases,  and  locate  the  points  K 
and  L  and  also  draw  the  line  MN.  Open  the  compass  to  the  required 
lap  and  find  by  trial  the  centre  I,  from  which  a  circle  may  be  described 
tangent  to  the  lines  OK  and  MN,  as  at  F  and  G. 

Next,  with  01  as  a  radius  and  0  as  a  centre,  describe  the  semi- 


250  THE  SLIDE-VALVE  AND  VALVE-GEAR 

circle  CID,  passing  through  I.  The  distance  CD  will  be  the  travel 
of  the  valve.  From  0  and  through  the  centre  I  draw  the  line  OP, 
and  BOP  will  be  the  required  angle  of  advance. 

There  is  still  one  other  case  where  this  diagram  can  be  used, 
where  we  know  the  point  of  cut-off,  the  lead,  and  the  amount  of 
port-opening  when  the  valve  is  at  the  end  of  its  travel,  and  we  wish 
to  find  the  lap,  the  valve-travel,  and  angle  of  advance. 

The  crank-pin  and  pistons  are  supposed  to  be  in  the  same  positions 
as  in  the  previous  cases,  and  the  cut-off  is  also  supposed  to  be  the  same. 

Draw  the  lines  OK  and  MN,  and  with  0  as  a  centre  and  a  radius 
OE  equal  to  the  known  port-opening,  describe  an  arc  of  a  circle. 
Next,  by  trial  find  the  centre  I  of  a  circle,  which,  when  described, 
will  be  tangent  to  the  arc  just  drawn,  and  which  will  also  be  tangent 
to  the  lines  OK  and  MN,  as  at  F  and  G. 

The  radius  of  the  circle  will  be  the  required  lap.  From  0  draw 
the  line  OP,  and  the  distance  BP  will  be  the  angle  of  advance. 
Through  I  draw  a  semicircle  with  a  radius  equal  to  01.  The  diam- 
eter CD  of  this  semicircle  will  be  the  distance  travelled  by  the  valve. 
In  all  of  the  above  cases  the  radius  OE  represents  the  amount  the 
port  will  be  opened  when  the  eccentric  is  on  its  dead-centre  or  at 
the  position  D.  Notice  also  that  the  crank  is  supposed  to  be  on  the 
dead-centre  at  A,  and  that  the  engine  is  about  to  make  the  forward 
stroke.  This  makes  it  necessary  to  lay  off  the  whole  geometrical  con- 
struction to  the  right  of  the  centre  0. 

The  measurements  for  the  other  stroke,  with  the  engine  on  the 
dead-centre  at  B,  will  have  to  be  constructed  to  the  left  of  the  centre 
0  and  below  the  line  AB.  The  measurements  for  this  stroke  will 
be  theoretically  the  same,  and  are  shown  by  the  dotted  lines. 

We  could  use  the  same  diagram  to  lay  out  the  movements  for  a 
piston-valve.  A  piston-valve,  to  cut  off  at  the  same  point  of  the 
stroke,  would  require  the  same  amount  of  lap;  and  if  the  nature  of 
the  work  done  by  the  engine  was  the  same,  it  would  require  the  same 
amount  of  lead. 

A  valve  is  said  to  be  direct  when  it  admits  the  steam  to  the  cyl- 
inder past  its  outside  edge,  and  allows  the  steam  to  exhaust  to  the 
atmosphere  past  its  inside  edge.  A  valve  is  said  to  be  indirect  when 
it  admits  the  steam  to  the  cylinder  past  its  inside  edge,  and  allows 
the  exhaust-steam  to  escape  past  its  outside  edge. 


THE  SLIDE-VALVE  AND  VALVE-GEAR  251 

These  are  the  conditions  of  a  piston-valve  whose  movement  is  just 
opposite  to  that  of  a  slide-valve.  Another  thing  to  be  noticed  is  the 
difference  in  the  movement  of  the  two  valves  relative  to  the  move- 
ment of  the  piston.  When  the  opening  movement  of  the  slide-valve 
occurs  the  valve  and  the  piston  both  move  in  the  same  direction. 

With  the  opening  movement  of  a  piston-valve  the  valve  and 
piston  move  in  opposite  directions  to  one  another.  This  makes  it 
necessary  to  shift  the  centre  of  the  eccentric  to~a  position  exactly 
opposite  to  that  of  a  slide-valve. 

THE     PISTON-VALVE 

The  use  of  the  piston-valve  has  been  largely  extended  of  late  years 
by  its  advantages  over  the  slide-valve  in  the  accessibility  of  its  parts, 
lightness,  more  perfect  balance,  and  greater  port-area,  which  features 
make  it  easier  to  handle,  and  decrease  the  wear  and  tear  on  the  motion- 
work  of  an  engine.  With  the  increased  size  of  engines  and  steam- 
pressure  the  ordinary  D  balance-valve  increases  in  size  proportion- 
ately, and  while  we  may  balance  a  slide-valve  in  the  same  ratio  as  the 
valves  on  smaller  engines,  the  difference  in  the  unbalanced  surface 
increases  with  the  size  of  the  engine,  and  with  it  the  wear  on  the 
valve,  link-motion,  and  eccentric-straps,  and  the  work  necessary 
on  the  part  of  the  engineer  to  handle  the  engine.  This  being  a  fact, 
a  great  deal  of  trouble  is  experienced  in  keeping  the  valves  on  slide- 
valve  engines  true  to  their  seats,  while  on  the  other  hand  there  is 
no  trouble  of  this  kind  with  the  piston-valve  until  after  the  engine  has 
been  in  use  for  a  long  while  and  the 
parts  have  become  badly  worn.  The  use 
of  the  inside  admission  piston-valve  does 
away  with  the  metallic  valve-stem  pack- 
ing, which  means  a  great  saving,  as  there 
is  only  the  exhaust-pressure  on  the  pack- 
ing side,  and  the  fibrous  packing  answers 
the  purpose  and  lasts  a  long  while. 

A  simple  piston-valve  taking  steam      FIG.  210.— Noye  piston-valve, 
at  its  ends  and  by  a  passage  through 

the  valve  is  used  on  the  Noye  engines,  and  shown  in  Fig.  210.     The 
valve  has  a  long  middle  bearing  and  rides  in  a  ported  sleeve,  forced 


252 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


into  the  cylinder  of  which  the  steam-chest  forms  a  solid  part.  The 
exhaust-ports  are  double,  thus  giving  a  long  bearing  to  the  valve. 
The  valve-rod  is  connected  direct  to  the  eccentric  and  its  rod  by  a  ball- 
and-socket  joint  to  correct  any  irregularity  in  the  alignment. 

Fig.  211  is  a  section  of  a  simple  hollow  piston-valve,  the  rod  of 
which  passes  through  a  central  tube  with  bar-stays  to  the  valve  and  a 
lining  to  the  valve-chest.  It  can  take  steam  at  the  centre  or  ends,  as 
convenient,  and  operates  exactly  as  a  D  slide-valve,  with  three  times 
its  extension  of  port-opening;  hence  short  ports  and  valve-travel. 


FIG.  211.— Hollow  piston- 
valve. 


FIG.  212. — Armington  &  Sims  double- 
ported  piston-valve. 


A  double-ported  piston-valve  in  use  on  the  Armington  &  Sims 
engines  is  shown  in  section  in  Fig.  212.  In  this  model  the  steam 
enters  the  steam-chest  between  the  valve-pistons.  It  will  be  seen 
that  steam-admission  is  through  two  ports  at  A  and  B  in  the  valve 
and  at  both  ends  simultaneously.  The  steam  entering  at  port  B 

passes  through  the  hollow  neck  of  the 
valve,  thus  duplicating  the  port-open- 
ing for  a  short  travel  of  the  valve.  For 
the  exhaust  the  valve  is  single-ported, 
but  the  great  width,  due  to  its  cylin- 
drical form,  gives  ample  port-opening 
with  a  short  travel  of  the  valve. 

In  Fig.  213  is  shown  a  section  of 
the  piston-valve  chest  and  the  valve 
used  on  the  Harrisburg  engine.  The 
pistons  of  the  valve  are  separate  from 
the  rod,  though  fastened  to  it  and 
made  adjustable  by  nuts  and  lock-nuts.  It  takes  steam  at  the  cen- 
tre and  exhausts  from  steam-chest  ports  outside  the  valve-disks.  It 
has  the  same  conditions  as  to  lap  and  lead  as  the  plain  slide-valve, 


FIG.  213. — Harrisburg  piston- 
valve. 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


253 


but  with  the  advantage  that  lap,  both  outside  and  inside,  may  be 
increased  by  changing  or  separating  the  parts  of  the  disks  with  a 
washer-disk  of  any  required  thickness. 


THE     SLIDE-VALVE     GEARAGE    AND     GOVERNORS 

The  plain  slide-valve  gear,  as  illustrated  on  page  225,  is  greatly 
modified  and  complicated  for  the  various  purposes  of  adjustment  to 
suit  the  needed  requirement  for  speed  and  reversing,  and  also  for 
obtaining  the  valve-motion 
without  the  eccentric. 

The  link  -  motion  from 
double  eccentrics,  much  in  use 
on  marine  engines  and  loco- 
motives, is  shown  in  Fig.  214. 
It  has  been  long  known  as  the 
Stephenson  link.  In  this  plan  FIG.  214. — stephenson  link, 

the  slotted  link  is  moved  up 

or  down  for  shifting  the  valve-motion  or  for  reversing  by  a  lever  and 
connecting-rod.  Its  design  has  many  forms  to  suit  the  varying  con- 
ditions of  this  plan  of  link-motion,  as  shown  in  Fig.  215,  and  is  largely 
in  use  in  its  simplest  form  on  the  engines  of  the  smaller  marine  craft, 

from  the  pleasure-boat  to  the  tug- 
boat, and  on  steam-driven  automo- 
biles and  traction-engines.  This  link- 
motion  is  used  in  connection  with 
ordinary  D  or  gridiron  valves,  with 
the  usual  lap  and  lead  for  from  five- 
eighths  to  three-quarters  cut-off. 

A  reversing  link-motion  from  a 
single  eccentric  is  shown  in  Fig.  216, 
in  which  the  slotted  link  is  pivoted  to 
the  end  of  the  eccentric-rod  and  is 
moved  up  and  down  by  a  bell-crank 
lever.  The  block  carrying  the  valve- 
rod  is  stationary,  allowing  the  pivoted 
,  ^  ^  i  link-centre  to  pass  by  it  and  thus 

FIG.  215.— Link  on  vertical  engine,    reverse  the  valve-motion.     There  are 


254 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


a  number  of  curious  models  of  valve-motion  from  single  eccentrics, 
of  which  we  select  the  following  as  examples  of  design  in  this 
interesting  line. 

A  method  of  lengthening  the  stroke  of  an  eccentric  of  small  size 
by  a  link-connection  to  the  eccentric-strap  at  a  right  angle  with  the 


FIG.  216. — Single-eccentric  reversing- 
gear. 


FIG.  217. — Method  of  increasing 
eccentric. 


connecting-rod  is  shown  in  Fig.  217.  In  this  way  a  considerable 
increase  in  the  throw  of  the  eccentric  can  be  made,  depending  upon 
the  relative  lengths  of  strap-arms.  A  variable  and  adjustable  throw 
of  a  single  eccentric — called  the  Fink  link-gear — for  a  D  valve  is  shown 
in  Fig.  218.  A  curved  slot-link  is  made  a  fixture  of  the  eccentric- 
strap,  as  shown,  one  end  of  which  is  pivoted  to  a  swinging  link 
attached  to  the  engine-frame.  The  end  of  the  jointed  valve-rod  is 
pivoted  to  a  block  in  the  link,  and  its  distance  regulated  by  a  con- 
necting-rod and  screw  pivoted  to  the  valve-rod  near  the  link. 


FIG.  218. — Direct  variable  valve-motion.         FIG.  219. — Variable  link  valve-motion. 

Another  and  simple  lever  and  link-movement  for  variable  expan- 
sion from  a  single  eccentric  is  shown  in  Fig.  219.  The  lever  is  pivoted 
to  the  connecting-rod  of  the  eccentric  and  travels  past  the  fixed  pivot 


THE   SLIDE-VALVE  AND  VALVE-GEAR 


255 


of  its  link,  thus  swinging  the  end  of  the  eccentric-rod  up  and  down 
for  the  valve-motion.  The  position  of  the  upper  end  of  the  lever  is 
adjusted  by  a  wheel  and  screw  for  varying  the  throw  of  the  valve. 
Many  variations  of  this  idea  have  been  pro- 
posed and  used. 

Another  design  of  past  usage  which  is 
illustrated  in  Fig.  220,  represents  but  one  of 
the  many  strenuous  efforts  to  utilize  the  sin- 
gle eccentric  for  the  most  efficient  and  eco- 
nomical work  of  the  valve.  Here  the  end  of 
the  eccentric-rod  is  pivoted  to  a  block  in  a 
slotted  link  that  by  tilting  up  or  down  with 
a  screw  varies  the  throw  of  the  valve,  the 
valve-rod  being  pivoted  to  the  eccentric-rod. 

The  Marshall  valve-gear,  shown  in  Fig. 
221,  is  operated  on  the  same  general  princi- 
ples as  the  last  two  examples.     A  single  eccentric,  set  opposite  to 
the  crank  and  its  short  connecting-rod,  is  pivoted  to  the  valve-rod 
at  J,  with  its  end  pivoted  to  a  link,  GF,  which  is  also  pivoted  to  a 
bell-crank  lever  at  G,  whose  length,  GH,  is  the  same  as  that  of  the 


FIG.  220.— Block-link  varia- 
ble valve-motion. 


FIG.  221. — Marshall  valve-gear. 

link  GF.  The  other  end  of  the  bell-crank  lever  is  pivoted  to  the  rod 
K  and  to  a  hand-gear  for  throwing  over  the  bell-crank  link  to  the 
position  at  G'  for  reversing  the  engine,  and  to  intermediate  points 
between  G  and  G'  for  varying  the  cut-off.  This  gear  gives  a  constant 
lead  for  both  positions.  The  position  of  the  gear  in  the  cut  is  for  run- 
ning "over." 


256 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


VALVE-GEARS  WITHOUT  ECCENTRICS 

The  idea  of  operating  a  steam-engine  without  an  eccentric  has  been 
a  theme  of  invention  for  a  long  time,  and  we  illustrate  those  that  have 
been  in  actual  use  and  made  a  name  for  themselves — the  Walschaert 
crank-pin  arm  and  the  Joy  valve-gear. 

One  of  the  Walschaert  valve-gears,  which  uses  an  eccentric,  but 
modifies  its  link -movement  by  a  cross-head  link  and  lever  for  making 

the  lead,  is  shown  in  Fig.  222.  The  ec- 
centric-rod is  pivoted  to  the  lower  end 
of  a  curved  slotted  link,  itself  pivoted  at 
its  centre  to  a  fixed  lug  on  the  engine- 
frame.  A  bell-crank  lever  governs  the 
position  of  the  end  of  the  valve-rod  and 
its  sliding  block  in  the  link.  An  arm 
from  the  cross-head  is  linked  to  a  lever 
connected  with  the  valve-rod  and  valve-stem  for  controlling  the  lead. 
Another  model  of  this  valve-movement,  as  used  on  the  compound 
locomotives  of  the  Italian  railways,  is  shown  in  Fig.  223.  The  crank- 
pin  arm  operates  the  motion  of  the  slotted  link.  The  valve-rod  block 
and  the  rod  are  balanced  by  a  weight  on  the  rock-shaft  arm  and 
operated  by  a  lever  connected  to  the  third  arm.  Valve-lead  is  made 
by  the  cross-head  arm-link  and  lever  connected  to  the  valve-rod  and 
link-block  rod. 


FIG.  222. — Walschaert  valve-gear 
with  eccentric. 


FIG.  223. — Walschaert's  locomotive  valve-geai  crank-pin  arm. 

A  novel  reversing-gear  without  eccentrics  is  shown  in  Fig.  224. 
The  valve-stem  is  connected  to  the  middle  of  a  short  link,  one  end 
of  which  are  pivoted  to  the  cross-head  bar  or  swinging-lever  sliding  in 
an  eye  or  sleeve-block  on  the  cross-head;  the  opposite  end  of  the 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


257 


link  is  pivoted  to  a  radial  bar  and  to  the  slide  on  the  link-block. 
This  block  receives  a  vertical  motion  from  a  sliding-block  on  the 
connecting-rod,  which  is  kept  in  position  by  a  rod  pivoted  on  the 
cylinder  -  head.  The 
cross-head  swinging- 
bar  imparts  a  move- 
ment to  the  valve- 
stem  equal  to  the  lap 
and  lead  of  the  valve. 
The  lateral  motion 


FIG.  224. — Reversing-gear. 


of  the  connecting-rod 
operates    the    throw 
and  reversal  of  the  valve  by  the  position  of  the  sliding-link  as  con- 
trolled by  a  hand-lever. 

A  floating  valve-gear7  used  on  the  reversing-ram  of  large  marine 
engines,  and  having  peculiar  features  in  its  movement,  is  shown  in  two 
positions  in  Fig.  225.  The  floating-lever  g  is  connected  to  the  cross- 
head  at  k,  and  pivoted  to  the  valve-rod  at  h  and  to  the  reverse- 
lever  rod  at  i.  The  piston-valve  is  indirect,  and  takes  steam  at  its 
centre.  When  the  lever  d  is  set  vertical  the  action  of  the  valve  sends 

the  piston  to  the  centre  of  the  cylin- 
der, and  when  pushed  over  sends  the 
piston  in  the  opposite  direction.  The 
springs  at  each  end  of  the  traverse-bar 
are  to  prevent  shock  by  the  sudden 
movement  of  the  piston. 

A  novel  valve-gear  has  been  ap- 
plied to  a  three-cylinder  engine,  illus- 
trated in  Fig.  226,  in  which  the  piston- 
valves  are  operated  by  a  connecting- 
rod  from  the  valve  to  the  trunk  of  the 
following  piston.  The  exhaust  is  dis- 
charged into  the  main  trunk  of  the  en- 
gine through  the  hollow  spool- valves, 
and  from  the  ports  opened  by  the 
trunk-pistons  into  jacketed  recesses.  Steam-connection  is  made  with 
the  chambers  at  the  head  of  each  cylinder. 

Another    curious    engine    is    the    "Brotherhood"    three-cylinder 


FIG.  225. — Floating  valve-gear. 


258 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


engine,  of  English  origin,  in  which  the  steam  enters  and  fills  the 
central  chamber  with  equal  pressure  on  all  the  pistons.  The  valve 
is  of  the  rotary-disk  type,  operated  by  the  crank-pin  within  the 


FIG.  226. — Three-cylinder  engine. 

chamber,  and  gives  steam  to  the  outside  of  the  pistons  alter- 
nately through  an  outside  port  to  each  cylinder.  The  steam-passages 
cover  the  shaft,  making  a  steam-tight  stuffing-box  necessary  on  the 
shaft.  Its  advantages  are  compactness  and  convenience  for  small 
powers,  but  it  lacks  efficiency. 


FIG.  227.—"  Brotherhood"  type 
of  three-cylinder  engine. 


FIG.  228. — Wolf  reversing-gear. 


In  regard  to  the  various  types  of  rotary  engines  and  the  hundreds 
of  different  models  and  valve-gear  motions  which  have  passed  the  or- 
deal of  trial  and  failure,  we  can  only  say,  from  our  own  experience  and 
knowledge  of  their  temporary  life,  that  the  rotary  principle,  as  de- 
veloped in  its  long  career,  has  finally  found  its  success  only  by  going 


THE  SLIDE-VALVE   AND  VALVE-GEAR 


259 


back  to  the  type  of  the  early  ages — the  simple  reaction  of  the  Hero 
and  Avery  models — with  the  addition  of  the  multiple  effect,  and  cul- 
minating in  the  modern  steam-turbine. 

The  reverse-gear  of  the  Wolf  model  is  another  form  for  reversing 
from  a  single  eccentric,  and  is  shown  in  Fig.  228. 

The  end  of  the  eccentric-arm  B  is  pivoted  to  a  block  in  the  slotted 
link  S,  which  is  also  shown  in  its  opposite  position  for  reversing  at  S'; 
the  valve-rod  R,  being,  connected  by  a  pivot  to  the  eccentric-arm 
at  a,  acquires  an  elliptical  motion  by  the  action  of  the  eccentric  and 
the  link-block,  which  becomes 
vertical  or  reversed  by  throwing 
over  the  link. 

A  most  novel  valve-gear  for 
a  triple-expansion  engine  from  a 
single  eccentric  is  used  on  the 
engines  of  the  Edison  Electric 
Company,  New  York  City,  and  is 
illustrated  in  Fig.  229.  The  eccen- 
tric-arm is  pivoted  by  a  link-arm 
to  the  frame  at  A,  which  carries  a 
pin  off  from  its  central  line,  and 
connects  with  the  high-pressure 
valve-rod.  The  bell-crank  lever 
B  is  pivoted  by  a  link  to  the 
lower  side  of  the  eccentric-strap, 
and  from  its  upper  arm  is  pivoted 
to  the  mean -pressure  cylinder 
valve-rod;  the  low-pressure  valve-rod 
through  a  rocker-shaft  and  arms  at  C. 


FIG.  229. — Triple-expansion  valve-gear. 


is  a  direct-line  connection 
This  is  the  most  ideal  con- 
ception for  operating  the  valves  of  a  triple-expansion  engine  yet 
brought  to  the  notice  of  the  author.  It  is  a  study  for  the  curious  in 
valve-gear  motion. 

A  valve-gear  derived  from  the  elliptical  motion  of  a  pin  near  the 
middle  of  the  connecting-rod  is  the  ideal  of  the  "Joy"  valve-gear 
movement.  The  ellipse  made  by  the  path  of  the  pin  is  symmetrical 
with  the  central  line  of  motion  in  the  engine;  but  the  action  of  the 
link-movement  slightly  changes  the  direction  of  its  axis  in  regard  to 


260 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


the  valve-motion.     Its  application  to  a  vertical  engine  is  shown  in 
Fig.  230,  with  a  screw-adjustment  for  the  position  of  the  link. 

In  Fig.  231  is  shown  the  same  arrange- 
ment applied  to  a  horizontal  engine,  with 
a  connecting-rod,  A,  extending  to  a  lever 
for  reversal. 


FIG.  230. — Vertical  valve-gear. 


FIG.  231. — Horizontal  valve-gear. 


In  Fig.  232  are  given  a  more  defined  diagram  and  description  of 
the  Joy  valve-gear. 

The  end  of  the  lever  abc  is  guided  by  the  rod  gc,  and  is  attached 

to  the  connecting-rod  at  a  point,  a, 
which  describes  an  ellipse,  having  the 
length  a\a2  equal  to  the  stroke  of  the 
piston.  This  ellipse,  which  is  omitted 
to  avoid  confusion,  is  symmetrical  with 
regard  to  the  axis  XX',  and  is  slightly 
more  pointed  at  the  crosshead-end  than 
at  the  crank-end. 

The  point  6,  which  describes  the 
irregular  ellipse  bbib2,  takes  the  place 
of  the  single  eccentric  used  on  other 
valve-gears,  and  acts  on  the  lever  bit 
while  e  is  guided  on  the  circular  arc  //i 
by  the  sliding-block  B,  and  the  point  e, 
which  describes  the  ellipse  ee\e2,  carries 
the  valve-rod  ed.  The  connecting-rod 
CD,  the  valve-rod  ed,  and  the  rod  eg 
are  in  the  same  plane;  the  levers  ac  and 
be  and  the  curved  guide-bars  //i  are 
double,  one  set  of  levers  being  on 
FIG.  232.— Joy  valve-gear  details,  each  side  of  the  connecting-rod.  In  the 


THE  SLIDE-VALVE  AND  VALVE-GEAR  261 

drawing  the  system  of  levers  in  front  of  the  connecting-rod  is  omitted 
to  show  the  construction  more  clearly.  The  point  i  could  be  guided 
on  the  arc  //i  by  a  link  centred  at  e.  Such  a  construction  is  used  in 
marine  engines. 

The  radius  of  the  guiding-link  //i  is  always  equal  to  the  length 
of  the  valve-rod. 

The  irregularity  due  to  the  angularity  of  the  lever  bie  is  com- 
pensated for  by  the  action  of  the  lever  ac,  somewhat  in  the  manner 
that  the  linkage  known  as  Watts's  parallel  motion  is  made  to  give 
nearly  a  straight  line  of  motion. 

The  guiding-bars  //i  are  hung  on  trunnions,  with  the  axis  at  the 
point  t'i,  and  are  connected  at  /  to  the  reversing-lever.  The  gear  is 
shown  in  full-gear  position  for  left-hand  rotation.  It  may  give  a 
shorter  cut-off  if  the  guiding-bars  //i  are  given  less  inclination  from 
the  horizontal  or  mid-gear  position,  and  when  in  mid-gear  it  will  give 
the  valve  a  motion  equal  to  the  lap  plus  the  lead;  and  when  the 
guiding-bars  //i  are  inclined  the  other  way,  the  engine  will  be  reversed. 

When  properly  proportioned  the  Joy  gear  gives  rapid  motion  to 
the  valve  when  opening  and  closing,  less  compression  at  short  cut-off 
than  does  the  link-motion,  and  the  cut-off  can  be  made  nearly  equal 
for  all  positions  of  the  gear.  Like  many  other  valve-gears,  it  gives 
constant  lead.  The  principal  defects  are  the  number  of  parts  and 
joints  that  are  liable  to  wear  loose,  and  the  obstruction  that  it  offers 
to  inspection  and  to  proper  care  of  the  crank-pin  and  cross-head 
when  the  engine  is  running. 

In  Fig.  233  are  shown  the  plan  and  vertical  section  of  the  Porter- 
Allen  medium  to  high-speed  engines,  made  by  the  Southwark  Foundry 
and  Machine  Company.  The  valve-gear,  which  is  of  the  four-port, 
balanced  slide-valve  type,  is  of  peculiar  interest,  not  only  in  the  fact 
of  having  four  slide-valves,  but  in  the  way  in  which  the  transmission 
of  motion  to  the  valves  from  a  single  eccentric  is  made.  The  steam- 
and  exhaust-valves  are  on  opposite  sides  of  the  cylinder,  and  are 
operated  from  a  single  eccentric  through  independent  rock-shafts. 

The  movement  of  each  valve  opens  or  closes  double-port  passages 
for  steam  and  exhaust,  as  shown  by  the  arrows  in  Fig.  234.  By  this 
construction  only  narrow  seats  and  short  valve-strokes  are  required 
to  give  large  port-openings.  The  arrangement  of  the  valve-gear  is 
clearly  shown  in  plan  and  elevation  in  Fig.  233.  The  eccentric  E  is 


THE  SLIDE-VALVE  AND  VALVE-GEAR 


263 


forged  on  the  shaft  and  is  coincident  with  the  crank.  The  eccentric- 
strap  and  the  curved  link  L  are  made  in  one  piece,  and  the  link. is 
pivoted  at  its  central  point  on  the  trunnions  t,  which  in  turn  are  pivoted 
to  the  frame  at  the  fixed  point  A.  The  vibration  or  horizontal  move- 
ment of  the  trunnions  is  equal  to  the  throw  of  the  eccentric.  In  the 
slot  of  the  link  is  the  block  B,  from  which  are  driven  the  two  steam- 
valves.  The  short  rock-shaft  s  on  the  frame  is  actuated  by  the  outer 
arm  a,  which  is  connected  by  the  steam-rod  with  the  block  in  the  link. 
It  carries  on  its  inner  end  the  two  arms  H  and  C,  which  drive  respec- 
tively the  head-end  and  crank-end  steam-valves,  through  the  medium 
of  the  two  rods  h  and  c,  and  the  two  valve-stems.  The  steam-valves 
are  offset  in  the  chest,  in  order  that  connection  to  each  valve  may  be 
made  at  its  centre;  and  short  guides  are  provided  at  the  connections 
of  the  rods  H  and  C  and  the  valve-stems. 

An  inspection  will  show  that  the  link  has  a  peculiar  movement, 
composed  of  the  horizontal  and  vertical  throws  of  the  eccentric. 
The  link  is  restrained  from  rising  by  the  trunnions,  and  the  horizontal 
throw  of  the  eccentric  draws  off  the  lap  of  the  valve,  while  the  vertical 
throw  tips  the  top  of  the  link  alternately  to  and  from  the  cylinder  as 
the  eccentric-centre  rises  or  falls  in  its  revolution,  the  upward  throw 
tipping  the  link  toward  the  cylinder  and  the  downward  throw  tipping 
it  from  the  cylinder. 
This  tipping  of  the  link 
opens  and  closes  the 
steam-valves  by  rock- 
ing the  rock-shaft  by 
means  of  the  steam-rod 
and  arm  a. 

In  Fig.  234  is  shown 
a  horizontal-plan  sec- 
tion of  the  cylinder  and 
steam-chests,  with  the 
double  port -opening 

for  both  steam  and  exhaust  at  the  commencement  of  the  forward 
stroke.  The  valves  are  opened  and  closed  quickly  by  the  middle  move- 
ment of  their  arms,  and  have  very  little  movement  while  open  or  closed, 
as  the  arms  are  then  at  the  extremes  of  the  travel.  The  position  of 
the  block  in  the  link  is  under  the  control  of  the  governor,  a  dropping 


FIG.  234. — Porter-Allen  cylinder. 


266  THE   SLIDE-VALVE  AND  VALVE-GEAR 

of  speed  causing  the  governor-balls  to  drop  and  so  raise  the  block,  and 
an  increase  of  speed  forcing  the  block  down  toward  the  trunnions. 
When  the  block  is  at  the  top  of  the  link,  the  steam-rod  receives  the 
full  tipping  motion  of  the  link,  and  cut-off  takes  place  at  the  maximum 
point,  about  six-tenths  of  the  stroke.  On  the  other  hand,  when  the 
governor-balls  are  in  the  extreme  upper  position  the  block  is  forced 
clear  down  to  the  trunnions,  and  so  receives  none  of  the  tipping 
motion  of  the  link.  Then  the  valve  is  merely  opened  for  lead,  and  is 
closed  immediately. 

Thus  the  steam-valves  are  always  opened  and  closed  quickly  at 
the  mid- travel  of  their  arms;  the  velocity  of  cut-off  increases  as  the 
cut-off  is  lengthened,  since  the  block  is  higher  in  the  link,  and  so  cor- 
responds to  the  increased  piston- velocity  near  mid-stroke;  and  the 
velocity  of  valve-movement  is  increased  directly  with  the  speed  of  the 
engine. 

The  Porter  fly-ball  governor  is  used.  It  is  carried  on  a  bracket 
from  the  engine-frame  and  is  belted  to  the  crank-shaft.  Its  distinguish- 
ing features  are  light  fly-balls  with  a  high  rotative  speed  to  secure 
sensitiveness,  and  a  heavy  ball  or  weight  on  the  vertical  shaft  to  secure 
the  gravity-effect  required  to  keep  the  revolving  balls  in  their  effective 
plane. 

Figs.  235  and  236  give  sketches  of  the  plan  and  sectional  elevation 
of  a  high-speed  tandem  compound  engine  direct  connected  to  a  multi- 
polar  generator.  The  slide-valves  of  both  cylinders  are  operated  from 
a  single  eccentric  with  a  rocker-arm  and  valve-rod  extension  through 
the  low-pressure  steam-chest,  on  the  end  of  which  is  an  arm  attached 
to  the  high-pressure  valve-rod,  with  adjustment  for  its  proper  opera- 
tion. 

The  receiver  is  simply  a  pipe-connection  from  the  exhaust  of  the 
high-pressure  cylinder  to  the  steam-chest  of  the  low-pressure  cylinder. 
The  cylinderrvolumes  are  so  proportioned  that  the  assigned  cut-off 
in  the  high-pressure  cylinder  will  equalize  the  gross  pressures  in  both 
cylinders  for  the  required  speed. 


CHAPTER   XVI 

THE     CORLISS     ENGINE 

IN  Fig.  237  is  shown  a  full-page  view  of  the  Corliss  engine,  with 
single  eccentric  and  the  usual  transmission-gear  for  operating  the 
valves,  and  with  the  names  of  the  various  connections,  the  details  of 
which  will  be  illustrated  in  the  following  pages. 

The  eccentric,  by  means  of  the  eccentric-rod,  rocker-arm,  and 
reach-rod,  causes  the  wrist-plate  to  oscillate  back  and  forth.  On  the 
wrist-plate  are  placed  the  steam-  and  exhaust-pins  which  operate  the 
steam-  and  exhaust-links  respectively.  These  links  operate  arms  at- 
tached to  the  valves.  The  exhaust-valves  are  attached  directly  to  the 
exhaust-arms,  and  they  rock  back  and  forth  with  the  wrist-plate, 
opening  and  closing  the  exhaust-ports  at  the  proper  time.  The 
steam-valves  are  operated  differently.  Each  steam-link  oscillates  a 
bell-crank,  which  is  loose  on  the  steam-valve  stem.  On  this  bell-crank 
is  a  latchirig-gear,  which  is  arranged  to  take  hold  of  a  steam-arm 
directly  attached  to  the  steam-valve.  As  the  bell-crank  moves,  the 
steam-valve  is  thus  made  to  follow  it,  and  thereby  open  the  steam-port. 

As  the  latch  on  the  bell-crank  moves,  it  reaches  a  stationary  knock- 
off  cam,  and  the  further  motion  of  the  bell-crank  forces  the  latch 
against  this  cam,  so  that  the  latch  is  released  and  the  bell-crank  can 
no  longer  pull  the  steam-arm  with  it.  The  steam-arm  is  always  acted 
upon  by  a  downward  pull  from  the  dash-pot.  Hence,  as  soon  as  the 
knock-off  cam  causes  the  latch  to  release,  the  steam-valve  is  pulled 
shut  by  the  dash-pot  and  cut-off  occurs.  The  position  of  the  knock- 
off  cam  is  changed  by  the  governor,  so  that  the  time  of  cut-off  varies 
with  the  load  on  the  engine,  in  order  to  keep  the  speed  constant. 

The  figure  shows  the  eccentric  in  the  lower  central  position — that 
is,  with  the  eccentric  vertically  downward.  Each  point  on  the  wrist- 
plate  is  then  in  the  centre  of  its  motion.  Arrows  indicate  the  directions 
in  which  the  various  parts  are  moving.  The  piston  has  very  nearly 
reached  the  crank-end  of  its  stroke,  and  the  crank-end  steam-valve 

267 


THE  CORLISS  ENGINE  269 

is  almost  ready  to  open,  in  order  to  admit  steam  to  drive  the  piston  on 
the  backward  stroke. 

The  amount  by  which  the  crank-end  steam-valve  closes  the  port 
in  the  position  shown  is  the  steam-lap.  The  head-end  steam-valve 
was  pulled  shut  by  the  dash-pot  some  time  before  the  position 
shown.  The  bell-crank  then  moved  to  the  end  of  its  travel  by 
itself,  and  it  is  now  going  back  again  after  the  steam-valve  in  order 
to  pick  it  up  and  cause  it  to  open  the  head-end~  steam-port  at  the 
proper  time. 

Since  the  wrist-plate  is  in  the  centre  of  its  motion  in  the  position 
shown,  the  crank-end  exhaust-valve  is  in  the  same  situation  as  is 
shown  for  the  head-end  exhaust-valve,  but  it  is  moving  in  the  opposite 
direction  with  respect  to  its  port,  and  is  therefore  just  closing  after 
having  caused  compression.  The  amount  by  which  the  exhaust- 
valves  close  the  ports  in  the  position  shown  is  called  the  exhaust-lap. 

Each  of  the  valves  moves  back  and  forth  as  the  eccentric  moves 
back  and  forth,  exactly  as  would  be  the  case  with  the  various  edges 
of  a  common  slide-valve.  There  is  a  distorting  effect  due  to  the  ob- 
liquity of  the  links  in  the  Corliss  gear,  but  this  merely  varies  the  speed 
with  which  the  valves  move.  Therefore  admission,  release,  and  com- 
pression are  effected  by  the  eccentric  in  very  much  the  same  way 
with  a  Corliss  valve-gear  as  with  a  common  slide-valve. 

In  all  descriptions  of  the  action  of  the  common  slide-valve  will  be 
found  reasons  for  the  use  of  lap  and  of  angle  of  advance.  For  the 
same  reasons,  a  Corliss  valve  has  lap  and  angle  of  advance.  The 
lap  of  a  slide-valve  is  the  amount  by  which  the  valve  closes  the  port 
when  both  eccentric  and  valve  are  in  their  central  positions.  The 
lap  of  a  Corliss  valve  is  the  amount  by  which  the  valve  closes  the  port 
when  the  eccentric  and  wrist-plate  are  in  their  central  positions. 
However,  the  valve  itself  is  not  then  in  the  centre  of  its  travel,  owing 
to  the  distorting  effect  of  the  motion  of  the  link  and  wrist-plate. 

The  eccentric  of  a  Corliss  engine  is  therefore  placed  ahead  of  the 
crank  by  90  degrees  plus  an  angle  of  advance.  In  Fig.  237  the  angle  of 
advance  is  the  angle  between  the  crank  and  the  horizontal  centre  line. 
The  latest  point  of  cut-off  is  somewhat  less  than  half-stroke.  The 
less  the  angle  of  advance  the  nearer  it  is  to  half-stroke.  Hence,  in 
order  to  increase  the  capacity  of  the  engine,  the  angle  of  advance  is 
made  as  small  as  possible.  This  is  done  by  making  the  percentages 


270 


THE  CORLISS   ENGINE 


of  compression  and  release  as  great  as  possible,  since  the  angle  of 
advance  is  determined  by  a  point  half-way  between  the  two. 

The  compression  must  occur  early  enough  to  give  a  proper  cushion. 
It  varies  from  90  to  98  per  cent.,  according  to  circumstances.  The 
release  must  occur  early  enough  to  give  a  proper  exhaust-lead.  The 
exhaust-lead  is  the  amount  that  the  exhaust-valve  is  open  when  the 
piston  starts  on  the  exhaust-stroke.  If  the  exhaust-lead  is  insufficient, 
the  exhaust  will  be  restricted  at  the  beginning  of  the  exhaust-stroke, 
giving  an  indicator-diagram  with  "turned-up  toes."  On  the  other 
hand,  a  too  early  release  must  be  avoided;  otherwise  the  end  of  the 

expansion-line  will  be 
lowered.  It  will  usual- 
ly be  found  that  if  re- 
lease occurs  at  from  98 
to  99  per  cent,  of  the 
stroke,  the  exhaust- 
lead  will  be  sufficient. 

The  details  of  the 
valves  and  valve-gear 
of  the  Corliss  type  are 
variable  to  a  great  de- 
gree, and  we  can  only  illustrate  a  few  of  the  leading  lines  of  design. 
In  Fig.  238  are  shown  two  forms  of  steam-valves  and  one  of  the 
exhaust-valve  in  general  use  with  a  single  eccentric.  The  stem  of  the 
uppermost  valve  is  mortised  vertically  into  the  valve,  which  gives 
the  valve  a  free  adjustment  for  perfect  seating.  The  stem  in 
the  middle  figure  passes  entirely  through  the  valve  with  rectangular 
bearings,  while  the  stem  of  the 
exhaust- valve  works  in  a  horizon- 
tal mortise. 

In  Fig.  239  are  shown  sections 
of  the  double-ported  steam-  and 
exhaust-valves  and  their  action, 


FIG.  238. — Corliss  valves. 


FIG.  239. — Double-ported  Corliss  valves. 


as  shown   by  the  arrows.     This 

model  of  valve   is   operated  by 

double  eccentrics  and  double  wrist-plates,  which  allows  a  greater  range 

of  cut-off  than  practicable  with  a  single  eccentric  and  single  wrist-plate. 


THE  CORLISS   ENGINE 


271 


The  single  eccentric  and  single  wrist-plate  allow  of  the  proper 
opening  and  closing  of  the  steam-  and  exhaust-ports  with  regard  to 
cut-off,  exhaust,  and  compression  for  a  cut-off  not  later  than  one-half 
to  five-eighths  of  the  stroke,  while  the  double  eccentric  and  double 
wrist-plate  give  a  possible  cut-off  at  nearly  full  stroke  in  case  of 
overload  on  the  engine. 

In  Fig.  240  is  shown  a  single-eccentric  valve-gear  with  overpull 
steam-  and  exhaust-links,  as  well  as  the  right-  and  left-threaded 


FIG.  240. — Single-eccentric  valve-gear. 

adjustment-couplings  and  lock-nuts,  and  in  Fig.  241  a  double  eccen- 
tric valve-gear  on  a  single  centre  with  overpull  steam-  and  exhaust- 
links. 

The  matter  of  arranging  the  links  and  bell-crank  movements  as 
to  overpull  or  underpull  of  the  links  and  the  bell-crank  action  depends 
much  upon  the  opinion  of  designers,  in  regard  to  the  velocity-stroke 
of  the  valve,  as  to  which  side  of  the  valve  may  be  considered  best  for 
steam-inlet  and  exhaust.  Four  or  more  bell-crank  valve-lever  posi- 
tions for  inlet  and  exhaust  are  in  use  by  the  leading  steam-engine 
builders  in  the  United  States. 

Fig.  242  shows  the  arrangement  of  the  single  wrist-plate  and  its 
link-rod  connections,  with  the  valve-levers  of  the  steam  side  turned 


272 


THE  CORLISS   ENGINE 


FIG.  241. — Double-eccentric  valve-gear. 

downward  and  those  of  the  exhaust  turned  upward.     The  position 
of  the  wrist-plate  and  valve-motion  is  in  the  middle  of  their  travel. 

In  Fig.  243  are  shown  an  elevation  and  plan  of  the  valve-motion, 
to  which  is  attached  Cite's  releasing-valve  gear.    A  is  the  valve-stem 


FIG.  242. — Fishkill-Corliss  valve-motion. 


THE  CORLISS   ENGINE 


273 


and  B  the  valve-lever,  and  CC'  a  bell-crank  which  vibrates  loosely  on  a 
sleeve  around  the  valve-stem,  and  is  connected  by  an  adjustable  link- 
rod  to  the  wrist-plate.  The  end  of  the  arm  C  carries  a  small  rock- 
shaft,  D,  which  has  a  hook,  E,  fastened  on  one  end.  This  hook  is 
provided  with  a  hardened  steel  catch-plate,  6,  which  engages  a  similar 
plate,  c,  fastened  on  the  end  of  the  valve-lever  B,  and  the  hook  is  kept 
in  place  by  a  light  spring,  /.  On  the  end  of  the  rock-shaft  D,  opposite 
the  hook  E,  is  fixed  a  forked  crank  F,  hav- 
ing a  pin  on  which  is  mounted  a  sliding- 
block  fitted  to  move  in  a  slot,  i,  of  a  link, 
G.  The  link  is  mounted  at  and  vibrates 
about  a  point,  j,  in  one  arm  of  a  bell- 
crank,  H,  and  the  bell-crank  oscillates 
upon  a  sleeve  around  the  valve-stem. 
The  other  arm  of  the  bell-crank  H  is  con- 
nected by  an  adjustable  rod,  Z,  to  the 
governor.  By  an  arrangement  not  shown, 
if  the  action  of  the  governor  become  de- 
ranged by  the  breaking  of  the  belt,  the 
sudden  dropping  of  the  governor-balls 
below  their  ordinary  limit  for  speed  re- 
verses the  releasing-gear,  and  the  block  in 
the  slide  i  is  pushed  out  and  prevents  the 
hook  E  from-  catching  the  valve-lever. 
In  the  ordinary  regulation  for  speed  the 
block  will  have  been  pushed  so  far  out- 
ward that  it  will  have  slightly  turned  the 
small  rock-shaft  D,  and  moved  the  hook 
E  enough  to  release  the  valve-lever  B. 
Then  the  dash-pot  will  act  and  close  the 
valve.  At  this  moment  of  release,  effected  by  the  toggle-like  action 
of  the  link,  the  pressure  on  the  bell-crank  H,  caused  by  the  liberation, 
will  be  exerted  in  a  radial  line  from  the  centre  of  the  slot  through  the 
point  j  to  the  centre  of  the  valve-stem  or  the  stand  which  supports  it, 
and  during  the  entire  movement  of  the  hook  E  there  will  be  no 
appreciable  strain  to  turn  the  bell-crank  H,  and  consequently  there 
will  be  no  strain  to  disturb  the  normal  action  of  the  governor.  As 
the  position  of  the  bell-crank  H  is  controlled  by  the  governor,  any 


FIG.  243. — Valve-gear  of  the 
Fishkill-Corliss  engines 


274 


THE  CORLISS   ENGINE 


change  in  the  height  of  the  governor  will  cause  a  change  in  the  posi- 
tion of  the  point  /,  and  a  corresponding  change  in  the  time  of  release. 
In  the  following  drawings  are  illustrated  the  conditions  and  limita- 
tions of  the  valve-action  hi  the  single-eccentric  Corliss  engine. 


FIG.  244. — Angle  of  advance. 

Fig.  244  shows  the  eccentric  set  at  its  angle  of  advance  and  the 
steam- valves  adjusted  for  the  lead,  with  the  crank-pin  on  the  inner 
dead-centre,  the  closed  ports  having  sufficient  lap  to  insure  a  steam- 
tight  joint. 


FIG.  245. — Point  of  cut-off. 


The  next  phase  is  the  point  of  cut-off,  shown  in  Fig.  245,  in  which 
the  steam-valve  of  the  forward  stroke  is  to  suddenly  close  from  a  full 
opening  at  one-third  stroke  by  the  release-gear  and  by  the  pull  of 
the  dash-pot  with  the  exhaust-valve  at  full  opening. 


FIG.  246. — Commencement  of  compression. 

The  last  phase  is  the  commencement  of  compression,  illustrated 
in  Fig.  246,  and  represented  at  about  one-sixth  of  the  stroke,  with  the 


THE  CORLISS   ENGINE 


275 


forward  exhaust-valve  just  closing  and  the  other  valves  entirely 
closed  with  their  proper  laps,  due  to  the  required  adjustment  of  steam- 
and  exhaust-valve  links. 

In  the  next  three  illustrations  (Figs.  247-249)  the  angle  of  ad- 
vance of  the  eccentric  is  set  at  a  less  angle,  say  about  100  degrees, 
from  the  inner  dead-centre  for  one-half  cut-off. 


FIG.  247. — Angle  of  advance. 

In  Fig.  247  the  eccentric  is  set  at  about  10  degrees  ahead  of 
a  right  angle  from  the  crank-pin  for  one-half  cut-off,  showing  the 
steam-valve  open  by  the  amount  of  its  lead  and  the  exhaust-valve 
just  opening. 


FIG.  248. — Point  of  cut-off  one-half. 

In  Fig.  248  the  point  of  cut-off  is  advanced  to  one-half  the  stroke, 
which  takes  place  at  the  extreme  throw  of  the  eccentric,  which,  with 
the  required  adjustment  of  the  links,  gives  a  release  of  the  steam-valve 
from  full  opening  and  with  a  full  opening  to  the  exhaust-valve. 


FIG.  249. — Commencement  of  compression 


276 


THE  CORLISS   ENGINE 


Fig.  249  shows  compression  slightly  less  than  in  the  first  set  of 
illustrations,  Figs.  244-246,  and  near  the  extent  of  the  action  of  a 
single  eccentric  for  the  best  efficiency  in  steam-distribution.  The  ad- 
vance of  the  eccentric  may  be  lessened  to  90  degrees  from  the  crank- 
pin,  or  given  a  negative  place  with  advance  of  the  cut-off  to  five- 
eighths,  but  with  restricted  port-openings,  which  can  only  be  given 
their  best  conditions  by  double-eccentrics  for  extended  cut-off  to 
meet  overload. 

For  the  benefit  of  students  and  others  interested  in  the  numerous 
designs  of  releasing-gear  for  Corliss  engines,  we  give  the  following 
illustrations  and  descriptions. 

A  standard  model  of  release-gear,  illustrated  in  Fig.  250,  is  that 
used  by  the  Fishkill  Machine  Company  and  others,  in  which,  A  being 
the  valve-stem,  a  bell-crank  operated  by  a  connecting-rod  from  the 


TO  WH.ST  PUTE 


FIG.  250. — Bell-crank  knock-off. 


FIG.  251. — Bass  release-gear. 


wrist-plate  lifts  the  grab-hook  E  and  the  valve-arm.  An  adjustable 
roller  at  R  releases  the  valve-arm,  which  is  pivoted  to  the  dash-pot 
rod  for  regulating  its  fall.  The  release-roller  R  is  operated  by  the  bell- 
crank  H  and  rod  Z  from  the  governor. 

The  release-mechanism  used  on  the  Bass  engines,  built  by  the 
Bass  Foundry  and  Machine  Company,  is  shown  in  Fig.  251,  in  which 
the  grab-hook  consists  of  a  block,  C,  sliding  in  a  grooved  slot  in  the 
bell-crank  lever  B,  B,  and  normally  forced  out  to  catch  the  block  on 
the  rocker-arm  at  D  by  a  spring.  The  block  C  carries  a  pin,  E,  on 
the  rear  side,  which  is  held  in  contact  with  a  cam-ring,  F,  having 
two  knock-off  dies,  M  and  N,  on  its  inside  surface.  As  the  bell-crank 
moves  in  the  direction  of  the  arrow  from  the  position  shown,  the 
roller  on  the  pin  E  strikes  the  cam-die  N  and  is  forced  rapidly  inward, 
releasing  the  drop-block  a. 


THE  CORLISS   ENGINE 


277 


FIG.  252.  —  Allis-Chal- 
mers  release-gear. 


The  release-gear  used  on  the  Allis-Chalmers  engines  is  shown  in 

Fig.  252.     The  hook  H,  which  is  forced  inward  by  the  spring,  engages 

with  the  valve-lever  B,  and  as  the  bell-crank  lever  A,  A  moves  in  the 

direction  of  the  arrow,  the  valve-lever  B  is  lifted 

and  opens  the  valve,  and  at  the  proper  moment, 

as  regulated  by  the  governor,  the  trip-lever  T 

comes  in  contact  with  the  projection  N  of  the 

cam  C,  forcing  it  and  the  grab-hook  outward 

and  releasing  the  drop-lever  B,  which  is  brought 

down  by  the  action  of  the  dash-pot. 

In  Fig.  253  are  shown  two  positions  of  the 
release-gear  used  on  the 
engines  of  the  Filer  &  S to- 
well  Co. 

In  this  design  B  is  the 

bell-crank,  which  carries  the  hook  H,  mounted 
on  a  short  shaft,  and  on  the  other  end  of 
which  is  the  trip-lever  (not 
shown),  which  engages  with 
the  knock-off  cam  C,  oper- 
ated by  the  governor-rod. 
K  is  the  drop-lever  with 
dash-pot  connection.  The 
cam-lever  C,  controlled  by 
the  governor,  limits  the 
time  of  release  by  the  hook 
H.  The  lower  figure  shows 

the  position  of  the  parts  at  the  moment  of  release. 
The  valve-gear  used  on  the  engines  of  the 

Nordberg  Manufacturing  Company  is  shown  in 

two  positions  in  Fig.  254,  similar  in  principle  to 

those  in  Fig.  253,  but  with  an  entire  change  in 

the  position  of  the  operating  parts.     The  curved 

bell-crank  B  carries  the  grab-hook  D,  mounted 

on  a  short  shaft,  and  having  an  arm  at  the  other 

end  with  a  trip-lever,  d,  which   rides  on  the 

knock-off  cam  A,  the  position  of  which  is  controlled  by  the  governor 

by  pushing  the  knock-off  cam  under  the  grab-hook  lever  for  release. 


FIG.  253.— Trip  valve- 
gear. 


FIG.  254.  — Nordberg 
valve-gear. 


278 


THE  CORLISS   ENGINE 


The  lower  figure  shows  the  position  of  the  parts  at  the  moment  of 
release. 

The  valve-gear  on  the  Sioux  City  and  other  engines  is  shown  in 
two  positions  in  Fig.  255.     It  consists  of  an  inverted  or  overhead 
wrist-plate  connection  of  the  bell-crank  lever 
with  a  forked  grab-hook,  in  which  A,  A  is  the 
GOVERNOR  bell-crank,  on  one  arm  of  which  is  pivoted  the 
forked  grab-hook  H,  held  by  the  spring  S,  the 
other  end  of  the  fork  riding  against  the  cam  C, 
the  movement  of  which  by  the  governor  releases 
the  valve-arm  B.     The  lower  figure  shows  the 
position  of  the  parts  at  the  moment  of  release. 

The  release-gear  of  the  Scottdale  Foundry 
and  Machine  Company  is  shown  in  front  and 
side  elevations  in  Fig.  256.  The  opposite  arm 
of  the  bell-crank  A  carries  the  latch-block  B, 
which  in  moving  forward  engages  the  block  C  on 
the  valve-arm  D,  to  which  is  also  attached  the 
dash-pot  rod.  The  latch-block  is  pressed  down 
by  a  spring  and  adjusting  thumb-screw  at  B, 
and  is  disengaged  by  the  cam  E  acting  upon  the 
lever  G  on  a  rock-shaft  in  the  valve-arm.  A  cam  at  J,  also  on  the 
governor-arm,  is  a  safety-cam,  and  lifts  the  lever  G  and  prevents  en- 
gagement of  the  latch- 
block,  if  the  governor- 
balls  should  fall  by  the 
breaking  of  its  belt. 

A  simple  and  effec- 
tive releasing-gear,  con- 
sisting of  few  parts,  is 
shown  in  Fig.  257.  It 
is  used  on  the  engines 
of  the  Watts-Campbell 
Company.  The  action  of 

this    gear   is   Well   shown  FlG.  256.— Scottdale  releasing-gear. 

in  the  cut,  in  which  A 

represents   the  crank-arm,  which  is  keyed  on  the   valve-stem   and 

carries  a  steel  catch-block  a,  which  is  fitted  into  the  end  of  the  crank- 


FIG.  255.— Sioux  City 
valve-gear. 


THE  CORLISS   ENGINE 


279 


ToGovemor_ 


arm  or  drop-lever.  B  is  the  bell-crank  lever,  one  arm  of  which  is 
connected  with  the  wrist-plate  by  the  rod  6.  In  the  other  arm  is 
fixed  the  pin  C,  which  carries  the  rocker-arm  D.  A  small  roller  e 
is  carried  at  the  upper  end  of  the 
rocker-arm  D,  and  is  held  against 
the  knock-off  cam  E  by  the  spring  c, 
as  shown. 

When  the  bell-crank  moves  in 
the  direction  of  the  arrow,  the  edge 
of  the  die-block  /  engages  the  end  of 
the  valve-arm  A,  and  raises  it  to  the 
point  of  release.  At  this  point  the 
roller  e  at  the  upper  end  of  the 
rocker-arm  D  comes  in  contact  with 
the  projection  of  the  knock-off  cam, 
which  forces  the  roller  and  upper 


FIG.  257. — Watts-Campbell  releasing- 
gear. 


end  of  the  rocker-arm  outward,  releasing  the  arm  A,  which  is  rapidly 
drawn  downward  by  the  dash-pot  and  the  rod  F. 

There  are  many  other  models  of  releasing-gear  in  use,  all  of  which 
involve  the  foregoing  principles;  but  enough  have  been  illustrated 
for  the  understanding  of  their  principles  of  action  to  meet  the  ordinary 
wants  of  engineers  in  engineering  possibilities,  such  understanding 
fulfilling  our  principal  aim. 


GOVERNORS     AND     DASH-POTS 

The  types  of  governor  best  suited  for  the  speed-regulation  of 
engines  of  the  Corliss  type  appear  to  be  those  of  the  fly-ball  and 
gravity-weight  combination,  although  other  models  are  in  use  which 
seem  to  give  satisfactory  control. 

In  Fig.  258  is  shown  the  leading  model  of  the  class  of  the  fly-ball 
gravity-governors,  the  Porter-Allen,  as  made  by  the  Southwark 
Foundry  and  Machine  Company.  It  consists  of  a  pear-shaped  weight, 
A,  moving  freely  on  the  spindle,  the  balls  B,  B  being  attached  to  the 
spindle  cross-bar  and  to  the  cross-bar  of  the  weight  by  rods  with  forked 
toggle-joints.  A  lever,  D,  pivoted  to  an  arm  on  the  governor-frame 
and  traversed  by  a  pin-connection  with  a  ring  in  the  grooved  sleeve 


280 


THE  CORLISS  ENGINE 


at  the  bottom  of  the  gravity-weight,  is  connected  to  the  valve-gear  at 
E  and  adjusted  by  a  counterweight  at  C. 

A  modification  of  this  governor  as  made  by  the  Watertown  Engine 
Company  is  shown  in  Fig.  259,  in  which  a  much  larger  movement 
of  the  lever  F  and  knock-off  cam-rods  E,  E  is  obtained.  The  upper 
yoke,  to  which  the  arms  of  the  governor-balls  are  pivoted,  is  fitted 
loosely  to  the  spindle,  the  latter  carrying  a  rack  with  which  mesh 
the  extensions  of  the  arms  to  which  the  balls  are  attached,  these  being 
in  the  form  of  a  sector  of  a  gear.  When  the  balls  fly  outward  the  ful- 


I 


FIG.  258. — Porter-Allen  governor. 


FIG.  259. — Watertown  governor. 


crum  of  the  arms  carrying  the  balls  is  raised  a  certain  distance,  which 
increases  the  height  of  the  central  weight  over  that  due  to  the  eleva- 
tion of  the  balls,  so  that  a  slight  change  in  the  position  of  the  balls 
will  cause  the  weight,  and  consequently  the  knock-off  cams,  to  move 
a  much  greater  distance  than  that  due  to  the  movement  of  the  balls 
only.  The  twofold  action  thus  obtained  makes  an  exceptionally 
sensitive  governor,  without  excessive  travel,  and  without  a  jerk  or  a 
tendency  to  fluctuate. 

The  governor  used  on  the  Lane  &  Bodley  engine  differs  materially 
in  its  generating  action  from  the  models  last  described  and  is  illustrated 
in  Fig.  260.  The  governor-balls  are  fixed  at  the  ends  of  bell-crank 
levers  which  are  supported  by  a  circular  plate.  The  horizontal  arms 


THE  CORLISS   ENGINE 


281 


of  the  bell-crank  levers  are  provided  with  rollers  for  the  purpose  of  re- 
ducing the  friction  between  them  and  the  collar  and  sleeve  which 
surround  the  spindle. 

The  outward  and  downward  movement  of  the  balls  is  resisted  by 
the  spring  which  opposes  the  upward  movement  of  the  sleeve.  At 
the  lower  end  of  the  sleeve  is  a  groove  in  which  is  fitted  a  collar  carrying 
one  end  of  the  bell-crank  lever,  to  which  is  attached  the  rod  operating 
the  knock-off  cams,  the  cam-connections  being  over  and  under  with 
a  continuous  rod.  It  will  be  noticed  that  a  very  slight  vertical  move- 
ment of  the  collar  will  move  the  lower  end  of  the  lever  and  the  governor- 
rods  a  considerable  distance.  The  speed  of  this  governor  is  about 
200  revolutions  per  minute,  which  renders  it  capable  of  producing  a 
great  change  of  centrifugal  force  for 
a  slight  variation  in  speed  and  with  a 
corresponding  insensibility  to  vary- 
ing internal  resistances.  While  the 
changes  in  position  are  made  very 
quickly,  there  is  no  jerk  or  vibration, 
for  the  dash-pot  at  the  base  of  the 
governor-post  prevents  a  very  sud- 
den upward  or  downward  movement 
of  the  spindle.  The  action  of  the 
automatic  stop  S  may  be  readiy  un- 
derstood, and  is  shown  in  its  work- 
ing position. 

When  the  engine  is  to  be  started, 

the  handle  on  the  stop  is  raised,  which  raises  the  governor-sleeve  by 
means  of  a  cam,  and  moves  the  knock-off  cams  on  the  valve-stems 
enough  to  allow  the  hook  to  engage  with  the  catch-hook. 

As  soon  as  the  governor  comes  up  to  speed,  the  governor-sleeve 
rises,  which  allows  the  weight  of  the  stop-handle  to  turn  the  cam  and 
bring  the  lower  face  under  the  sleeve,  so  that,  should  the  governor  stop, 
the  sleeve  will  descend  low  enough  to  allow  the  knock-off  cam  to 
prevent  the  hook  from  engaging  with  the  catch-block,  thus  insuring 
against  the  opening  of  the  valves. 

In  Fig.  261  is  represented  the  slow-speed  governor  used  on  the 
Scottdale  Corliss  engine.  Its  lifting-power  is  augmented  by  the 
lever-connections  on  long  arms  and  light  balls,  which,  at  a  low  velocity, 


FIG.  260. — Lane  &  Bodley  governor. 


282  THE  CORLISS  ENGINE 

about  60  revolutions  per  minute,  give  sufficient  lifting-power  to  oper- 
ate the  gravity-weight.  The  bell-crank  is  connected  to  the  sliding- 
sleeve  by  a  short  rod,  and  upon  the  other  end  of  its  shaft  are  fixed  a 
lever  and  its  adjusting  weight.  A  retarding  annular  dash-pot  around 
the  spindle  regulates  the  action  of  the  balls  and  also  catches  the  oil 
dripping  from  the  collars.  The  governor  is  also  provided  with  an 

automatic  safety-stop,  supported,  when  not 
in  action,  by  the  governor-belt,  and  requir- 
ing no  attention  when  the  engine  is  started 
or  stopped. 

Of  the  great  variety  of  pulley-  or  fly- 
wheel governors  there  seem  to  be  two  classes 
as  regards  manner  of  movement  of  the  ec- 
centric, one  of  which  consists  in  shifting 
the  eccentric  and  the  other  in  rotating  the 
eccentric  on  a  fixed  centre.  The  mech- 
anism for  obtaining  these  movements  is 
mostly  of  the  centrifugal  order,  but  in- 
ertia and  positive  mechanical  devices  are 
also  in  use. 

Of  the  shifting  eccentrics,  we  illustrate 
in  Fig.  262  the  simple  device  used  on  the 
Sweet  straight-line  engine.  In  this  gover- 
nor the  slotted  eccentric  has  two  opposite 
arms,  one  end  of  which  is  pivoted  to  an 
arm  of  the  pulley  or  fly-wheel,  and  the 
other  to  a  link,  moved  by  a  lever  and  by 
the  centrifugal  action  of  a  weight,  and 
restrained  by  a  leaf -spring. 
FIG.  261.— Scottdale  governor.  In  Fig.  263  is  shown  another  design  of 

shifting  eccentric.     In  this  the  two  weights 

are  connected  for  equal  movement  by  a  link,  and  each  balanced  by  a 
helical  spring.  The  eccentric-arm  is  pivoted  to  an  arm  of  the  pulley 
or  fly-wheel  and  also  to  the  end  of  one  of  the  weights,  so  that  excess 
of  speed  throws  the  eccentric  toward  its  centre  of  rotation. 

In  Fig.  264  is  shown  the  pulley-governor  used  on  the  engines  of 
the  Fitchburg  Steam  Engine  Company.  It  will  be  seen  that  when  the 
weights  c,  c,  respectively,  are  moved  outward  by  centrifugal  force, 


THE  CORLISS  ENGINE  283 

they  draw  the  eccentric  across  the  shaft  by  means  of  the  links  d,  d. 
The  weights  e,  e  are  for  the  purpose  of  counterbalancing  the  weight  of 
the  eccentric-strap  and  one-half  the  weight  of  the  eccentric-rod  in  hori- 
zontal engines,  and  the  total  weight  of  these  members  in  vertical 


FIG.  262. — Sweet's  governor.  FIG.  263. — Shifting  eccentric-governor. 

engines,  which  leaves  no  work  upon  the  governor-weights  but  to  shift 
the  eccentric  when  the  load  upon  the  engine  changes.  The  springs 
oppose  the  outward  movement  of  the  governor-weights  c,  c,  by  means 
of  which  the  speed  of  the  engine  may  be  changed. 

It  will  be  apparent  that  by  tightening  the  springs  the  speed  of 
the  engine  may  be  increased,  and  by  loosening  them  the  opposite 
result  will  be  obtained.  The  maximum  range  of  cut-off  is  from  zero 
to  three-fourths  stroke,  which  enables  the  engine  to  maintain  a  uniform 
speed  under  wide  variations  of  load. 

Of  the  rotating  eccentric-governors  there  are  a  number  of  designs, 

a  few  of  which  we  select  to  show  the 
main  points  of  variation. 

In  Fig.  265  is  shown  the  pulley- 
governor  used  on  the  Buckeye  engine, 


FIG.  264. — Fitchburg  pulley-governor.       FIG.  265. — Rotating  eccentric-governor. 

in  which  the  centrifugal  force  of  two  pivoted  weights  connected  to  a 
spiral-slotted  face-plate  by  the  links  D,  D  oscillates  the  face-plate. 
An  arm,  E,  on  the  eccentric  carries  an  adjustable  wrist-pin  by  which 


284 


THE  CORLISS  ENGINE 


the  eccentric  is  rotated,  and  on  an  extension  of  the  arm  on  the  other 
side  of  the  eccentric  is  a  wrist-pin  which  allows  of  a  reversion  of  the 

eccentric. 

In  Fig.  266  is  shown 
the  governor  of  the  Mc- 
Intosh  &  Seymour  Co.  on 
their  multiported  four 
slide-valve  engines.  In 
this  governor  the  cut-off 
eccentric  is  free  to  re- 
volve on  the  shaft,  and  is 
connected  to  the  weights 
c,  c  by  the  links  d,  d. 
The  outward  movement 
of  the  weights  is  resisted 
by  the  leaf-springs  e,  e, 
while  any  tendency  to 
sudden  fluctuations  in 


FIG.  266. — Dash-pot  governor. 


the   position   of  the 
weights  is  prevented  by 

the  dash-pots  /,  /.  The  ends  of  the  springs  are  connected  to  the 
weights  by  means  of  telescopic  pins,  g,  g;  lengthening  these  pins  in- 
creases the  compressive  effect  of  the  spring,  and  thus  offers  greater 
resistance  to  the  weights.  To  increase  the 
sensitiveness  of  the  governor,  therefore, 
these  pins  must  be  lengthened,  and  if  the 
governor  is  too  sensitive  they  must  be 
shortened.  The  circular  openings  in  the 
weights  are  provided  with  extra  weights  in 
the  form  of  bushings.  The  speed  of  the 
engine  is  changed  by  changing  these  bush- 
ings, inserting  heavier  ones  when  the  speed 
is  to  be  reduced  and  lighter  ones  when  it  is 
to  be  increased. 

In  Fig.  267  is  shown  an  inertia-governor,  in  some  designs  of  which 
the  momentum  of  the  weights  and  the  centrifugal  force  are  combined 
factors  in  the  operation  of  varying  the  position  of  the  eccentric,  either 
by  rotation  or  by  shifting  it  from  its  centre.  The  illustration  shows 


FIG.  267. — Inertia-governor. 


THE  CORLISS   ENGINE 


285 


the  inertia-governor  used  on  the  Leffel  engine.  The  weights  B,  B'  are 
balanced,  with  their  centre  of  gravity  at  the  centre  of  the  engine-shaft, 
but  pivoted  at  A  to  the  fly-wheel,  and  by  an  arm  to  the  eccentric  at  p. 
The  spring  K  holds  the  weights  to  their  normal  position,  their  range 
of  motion  by  differential  momentum  from  variable  speed  of  the  engine 
being  limited  by  the  stops  on  the  rim  of  the  fly-wheel  or  pulley. 


THE     VACUUM     DASH-POT 

The  dash-pot  is  one  of  the  most  essential  adjuncts  of  the  Corliss 
type  of  engine.  The  speed  and  softness  of  the  valve-closure  are  due 
to  the  perfect  action  of  the  dash-pot,  and  as  there  are  several  designs 
in  use  we  illustrate  some  of  their  features  and  manner  of  action. 

In  Fig.  268  is  shown  a  section  of  the  dash-pot  used  on  the  Frick 
engine.  It  is  a  dustless  dash-pot,  as  the  air  that  is  drawn  under  the 
piston  in  its  upstroke  is  exhausted  into  the  same  annular  chamber 
from  which  it  is  taken,  which  also  renders  the 
dash-pot  noiseless  in  operation.  As  the  plunger 
P  is  drawn  upward  by  the  valve-gear,  air  is 
drawn  into  the  plunger-cylinder  from  the  annular 
chamber  A,  through  the  check-valve  c.  The  air 
is  not  sufficient,  however,  to  prevent  the  for- 
mation of  a  partial  vacuum,  which  draws  the 
plunger  quickly  downward  when  the  valve- 
spindle  is  released.  As  the  plunger  nears  the 
bottom  of  the  cylinder  it  is  cushioned  by  the  air, 
which  is  forced  back  into  the  outer  chamber 
through  the  poppet-valve  V.  The  degree  of  cushioning  can  be  accu- 
rately adjusted  by  means  of  the  screw  S. 

In  Fig.  269  is  shown  in  section  and  elevation  the  dash-pot  used 
on  the  Watts-Campbell  engines.  This  dash-pot  is  very  simple,  and 
consists  of  a  cup-cylinder  having  a  tapered  lower  portion  which  sur- 
rounds the  plunger,  as  shown.  The  plunger  is  made  to  fit  over  the 
central  column  in  the  cylinder,  so  that  when  the  plunger  is  drawn 
upward  a  partial  vacuum  is  formed  in  the  space  between  the  plunger 
.and  the  column.  The  annular  space  around  the  piston-end  of  the 
plunger  allows  a  free  fall  of  the  plunger  by  the  vacuum  effect  until 


FIG.  268.— Frick  dash- 
pot. 


286 


THE  CORLISS   ENGINE 


it  reaches  the  taper  closure  near  the  bottom  of  the  cup-cylinder. 
The  cushioning  effect  is  produced  by  the  escape  of  the  air  from  the 
annular  space  at  the  bottom  of  the  cylinder,  which  continues  until 
the  plunger  reaches  the  straight  portion  of  the  bore. 


FIG.  269. — Cup-cylinder  dash-pot. 

The  remainder  of  the  air  thus  entrapped  is  expelled  through  the 
small  valve,  which  offers  greater  or  less  obstruction  to  the  small  exhaust- 
port  shown  at  the  bottom.  A  spring  check-valve  in  the  head  of  the 
central  column  is  an  air-relief,  and  the  small  screw  at  the  top  regulates 
the  vacuum. 


SETTING     THE    VALVES     AND      GEAR      OF    A 
CORLISS     ENGINE 

Every  engineer  on  taking  charge  of  a  Corliss  type  of  engine  should 
have  at  hand  a  detailed  description  of  its  special  action  and  govern- 
ment, with  directions  of  the  builders  for  setting  and  adjusting  the 
valves  and  valve-gear.  The  variety  of  motions  and  kinks  in  regard 
to  the  setting  and  proper  adjustment  of  valves  and  gear,  including 
rods,  links,  eccentric,  governor,  and  dash-pots,  differs  so  much  in 
details  of  design — although  the  general  principles  of  operation  are 
essentially  alike— that  only  a  general  description  and  illustration  for 
setting  the  valves  and  valve-gear  can  be  attempted  here.  It  is 
hoped  that  they  may  be  useful  as  an  aid  to  the  new  engineer  when 
special  instructions  are  not  at  hand. 

With  the  first  examination  of  the  engine  to  find  if  every  part  of 


THE  CORLISS   ENGINE 


287 


its  running-gear  is  in  working  order,  see  that  the  builders'  marks  on 
the  valves  and  cylinder,  as  also  those  on  the  wrist-plate  hub,  are  in 
alignment  when  the  wrist-plate  is  on  its  central  position  and  the  centre 
line  of  the  rocker-arm  is  in  a  vertical  position,  as  shown  in  Fig.  270, 
with  the  eccentric  at  right  angles  to  the  central  line  of  the  engine  and 
the  crank-pin  following  the  right  angle  plus  the  lead.  The  reach-rod 
and  eccentric-rod  being  both  adjustable,  any  variation  from  the  proper 
position  may  be  readily  made. 

In  this  position,  on  removal  of  the  back  bonnets  the  builders' 
marks  on  the  end  of  the  valve  and  cylinder  will  indicate  the  opening 


i  I 


FIG.  270  — Central  position  of  the  wrist-plate  and  rocker-arm. 

edge  of  the  valve  and  port  and  the  lap.  On  the  shoulders  of  the 
wrist-plate  and  its  pin  find,  or  make,  a  mark  like  b  a  in  Fig.  271,  which 
should  coincide  with  the  central  position  of  the  wrist-plate. 

Set  the  wrist-plate  in  its  central  position  by  an  extra  washer 
under  the  nut  of  the  wrist-plate  pin,  and  then  adjust  the  valves  for 
their  proper  positions  by  regulating  the  link-length  for  each  valve. 
Then  by  turning  the  wrist-plate  to  its  extreme  positions,  as  shown  in 
Fig.  272,  connect  the  dash-pots  so  that  when  down  the  hook  will  catch 
with  sufficient  room  to  insure  locking. 

The  governor  should  be  blocked  up  to  about  the  running  position, 
to  allow  of  the  free  action  of  the  release  at  this  position  of  the  governor- 
cam. 

The  wrist-plate  should  be  turned  from  one  extreme  position  to 


288 


THE  CORLISS   ENGINE 


the  other,  so  as  to  open  the  valves  alternately  and  allow  the  dash-pot 
plungers  to  seat  properly,  and  in  order  so  that  the  hooks  may  engage 
the  catch-blocks  without  fail  when  the  wrist-plate  is  rocked  to  its  ex- 
treme positions.  Hook  the  reach-rod  onto  the  wrist-plate  with  the 
eccentric  nearly  in  its  extreme  position,  and  adjust  its  length  so  that  the 
lines  on  the  wrist-plate  hub  will  nearly  coincide.  Adjust  the  length 
of  the  governor-rod  corresponding  to  the  valve — which  is  now  open — 
so  that  the  inner  member  of  the  hook  just  engages  the  projection 
on  the  knock-off  cam.  Move  the  wrist-plate,  by  turning  the  eccentric, 


FIG.  271. — Wrist-plate  in  its  cen- 
tral position  on  the  centre. 


FIG.  272. — Extreme  positions  of  the  wrist-plate. 


until  the  lines  on  the  hub  coincide.  The  valve,  which  has  been  raised, 
should  now  be  released  and  the  dash-pot  plunger  properly  seated. 
The  governor-rod  should  be  so  adjusted  that  the  steam-valve  may 
be  released  by  the  time  the  wrist-plate  reaches  the  extreme  position, 
in  order  to  insure  the  valve  being  closed  when  the  latest  point  of  cut-off 
is  reached,  which  point  corresponds  to  the  extreme  position  of  the  wrist- 
plate  and  eccentric,  and  to  the  governor  in  its  lowest  operative 
position,  viz.,  with  the  collar  or  sleeve  resting  on  the  safety-stop. 
The  governor-rod  at  the  opposite  end  of  the  cylinder  should  be  similarly 
adjusted. 

As  the  valve-ports  open  on  the  inside  or  outside  in  different  engines, 
the  positions  of  the  builders '  marks  on  the  valves  must  be  considered 
by  a  reversal  of  the  positions  of  their  connections. 

Having  made  the  adjustment  of  the  steam-valves,  treat  the 
exhaust-valves  in  the  same  way,  with  the  exception  of  the  amount  of 
lap,  which  should  be  negative. 

The  following  table  shows  the  usual  practice  for  lap,  lead,  and 
exhaust-release  for  various  sizes  of  Corliss  engines,  which  may  be 
variable  to  suit  the  methods  of  different  designers: 


THE  CORLISS  ENGINE 


289 


TABLE  XXXIV. — LAP,  LEAD,  AND  EXHAUST-RELEASE. 


Size  of  engine. 

Revolutions  per  minute. 

Steam-lap, 
inch. 

Steam-lead, 
inch. 

Exhaust- 
release,  inch. 

12X36-48 

90-85 

ft 

ft 

^ 

14X36-48 

85-75 

.-v 

& 

16X32-48 

85-75 

ft 

3-V 

ft 

18X36-48 

80-75 

1 

-6\ 

ft 

20X42-60 

75-65 

I 

£ 

ft 

22X42-60 

75-65 

if 

S~ 

ft 

24X42-60 
26X48-60 

75-65 
70-65 

t 

1 

* 

28X48-72 

65-55 

if 

-eV 

3% 

30X48-72 

65-55 

if 

£ 

1 

32X48-72 

65-55 

i 

*V 

i 

34X48-72 

65-55 

I 

ft 

i 

36X48-72 

62-55 

tf 

A 

i 

38X60-72 

60-55 

if 

£ 

-      ft 

40X48-84 

60-55 

ft 

-3\ 

ft 

42X48-72 

70-55 

ft 

31? 

ft 

In  Fig.  273  is  shown  a  sketch  of  a  Corliss  engine  of  the  Hamilton 
design,  with  single  wrist-plate  and  trip  valve-gear,  governor,  and  dash- 
pots.  The  lap-movement  of  the  steam-valves  is  outside  or  toward 
the  ends  of  the  cylinder.  The  exhaust-valves  open  on  the  inside 


FIG.  273. — Hamilton  Corliss  engine. 

or  toward  the  centre  of  the  cylinder.  A  stop-motion  is  carried  by 
the  governor  for  preventing  a  runaway  in  case  the  governor-belt 
should  break. 

A  tandem  compound  Corliss  engine  of  the  Atlas  type  is  sketched 
in  Fig.  274.     The  steam-valve  gear  of  this  engine  for  both  high-  and 


290 


THE  CORLISS   ENGINE 


low-pressure  cylinders  has  a  through  line  of  connecting-rods  from 
one  eccentric  and  a  through  line  of  connecting-rods  from  the  other 
eccentric  to  the  valve-arms  on  each  cylinder.  The  governor  controls 


FIG.  274. — Tandem  Corliss  engine. 

the  steam-  valves  of  the  high-pressure  cylinder,  which  open  on  the  inside 
or  toward  the  centre  of  the  cylinder. 

In  Fig.  275  is  shown  a  sketch  of  the  cylinder  and  valve-gear  of  the 
Corliss  engine  of  the  C.  &  G.  Cooper  design,  with  two  wrist-plates  and 


FIG.  275. — Cooper  Corliss  engine. 

two  eccentrics  whose  rods  are  transmitted  to  the  valve-gear  through 
two  rocker-arms. 

The  question  of  a  right-  and  left-handed  engine  is  often  raised,  and 


THE   CORLISS   ENGINE 


291 


occasionally  has  been  the  subject  of  serious  discussion.     In  Fig.  276 
we  give  a  sketch  from  good  authority  as  to  the  positions  of  a  right-  and 


FIG.  276. — Left-handed  and  right-handed  engines. 

a  left-hand  engine.  When  standing  at  the  cylinder  and  looking  toward 
the  shaft,  a  right-hand  engine  has  the  valve-gear  on  the  right-hand 
side,  and  vice  versa. 


CHAPTER    XVII 


COMPOUND    ENGINES 

THE  simple  compounding  of  the  steam-engine  is  a  source  of  econ- 
omy over  the  single-cylinder  non-condensing  type  wherever  water  for 
condensation  cannot  be  made  available.  The  simple  condensing- 
engine  was  formerly  the  most  important  step  in  the  progress  of  steam- 
power,  until  followed  by  the  multicylinder  compound  condensing  type, 
of  which  simple  compounding  is  probably  the  most  economical  method 
of  developing  power  from  high-pressure  steam  where  condensing  water 
is  not  available.  This  system  is  now  being  largely  adopted  for  loco- 
motive service  and  for  localized  power  as  a  means  of  greater  expansion 
from  higher  pressure  and  with  high  speed.  The  loss  by  cylinder- 
condensation  is  lessened  by  compounding,  as  is  approximately  shown 
in  the  following  table: 

TABLE  XXXV. — PERCENTAGE  OF  Loss  BY  CYLINDER-CONDENSATION. 


Percentage  of  stroke 
completed  at  cut-off. 

Simple  engines. 

^asss,*,. 

5 

42 

10 

34 

26 

15 

29 

24 

22 

20 

26 

22 

20 

30 

22 

18 

16 

40 

18 

15 

13 

50 

14 

12 

10 

The  water-consumption  in  a  compound  engine  as  compared  with 
a  single-cylinder  non-condensing  engine  is  shown  approximately  in 
the  following  table,  general  conditions  only  being  considered: 

The  value  in  compounding  the  expansion  of  steam  for  power 
has  been  amply  shown  in  a  practical  way  by  the  experience  of  the 
past  two  decades,  in  which  its  multiple  effect  reached  its  fourth  stage; 
further  advance  in  this  line  seems  impracticable  from  the  near  safety- 
limit  of  boiler-pressures  to  the  tensile  strength  of  material  for  practical 
and  economic  construction. 

292 


COMPOUND  ENGINES 


293 


TABLE    XXXVI. — WATER-CONSUMPTION    IN     COMPOUND    AND    SINGLE-CYLINDER 

ENGINES. 


Cut-off, 
per  cent. 

Initial  pressure  by  gauge. 

Mean  effective  pressure 
gauge. 

Feed-water 
per  indicated 
horse-power 
per  hour, 
pounds. 
Compound 
engine. 

Feed-  water  per 
indicated 
horse-power 
per  hour, 
pounds. 
Single  cylinder. 

High-pressure 
cylinder, 
pounds. 

Low-pressure  High-pressure  Low-pressure 
cylinder           cylinder,           cylinder, 
pounds.             pounds'.           J^oTut 

• 

( 

80 

4.0 

11.67 

2.65 

~-16.92 

29.88 

10     ] 

100 

7.3 

15.33 

3.87 

15.00 

25.73 

( 

120 

11.0 

18.54 

5.23 

13.86 

21.60 

( 

80 

4.3 

26.73 

5.48 

14.60 

25.68 

20     ] 

100 

8.1 

33.13 

7.56 

13.67 

23.77 

( 

120 

12.1 

39.29 

9.74 

13.09 

21.86 

( 

80 

4.6 

37.61 

7.48 

14.99 

26.29 

30     \ 

100 

8.5 

46.41 

10.10 

14.21 

24.68 

( 

120 

11.7 

56.00 

12.26 

13.87             23.07 

The  liability  to  self-destruction  in  both  boiler  and  engine  is  very 
great,  as  is  also  their  cost  at  the  highest  pressure  now  in  use — say, 
200  pounds  per  square  inch. 

The  experiments  of  Perkins  in  England  many  years  since  with 
steam  at  250  pounds  pressure  for  power  purposes,  ended  in  practical 
failure,  and  was  followed  by  Reed  and  others  in  the  United  States 
with  like  results.  Steam  at  1,000  pounds  pressure  was  used  by  Per- 
kins, and  was  repeated  by  the  author  in  New  York  with  a  Perkins 
gun,  with  practical  failure  as  to  its  merit;  and  all  these  lessons  are 
probably  lost  to  the  present  ambition  of  the  engineering  world. 

Below  a  limited  high  pressure  the  economy  of  compounding  or 
multiple  expansion  is  found  in  a  reduction  in  the  size  of  parts — making 
a  lighter  and  less  costly  engine  for  a  given  power;  giving  in  a  two-  or 
three-crank  engine  a  more  uniform  twisting  or  turning  moment,  with 
smaller  strains  in  the  engine;  enabling  a  smaller  fly-wheel  and  its  strain- 
ing moments,  and  resulting  in  a  more  uniform  motion  where  a  fly-wheel 
is  not  used — and  in  making  the  range  of  temperature  less  in  each 
cylinder,  and  thereby  lessening  the  total  loss  in  steam  per  indicated 
horse-power. 

The  highest  efficiency  of  the  compound  non-condensing  engine 
requires  a  proportion  of  cylinder-volumes,  initial  pressure,  and  cut-oft 
that  will  give  the  terminal  pressure  in  the  low  pressure  at  from  2  to  3 
pounds  above  the  atmosphere. 


294 


COMPOUND  ENGINES 


The  compound  non-condensing  engine  has  two  phases  in  its  action, 
one  of  which  is  a  direct  discharge  from  the  high-pressure  cylinder  to 
the  low-pressure  cylinder,  as  in  the  Woolf  type;  the  other  has  a  receiver 
between  the  cylinders.  Of  the  first,  the  Westinghouse,  Buckeye,  and 
Ball  engines  are  examples;  but  these  may  be  made  condensing  by  a 
small  change  in  cylinder-volumes. 

The  relative  areas  of  the  high-  and  low-pressure  cylinders  for 
non-condensing  and  condensing  compound  engines  of  the  Buckeye 
Engine  Company  are  here  given  for  various  pressures  in  their  tandem 
type. 


TABLE  XXXVII. — CYLINDER  PROPORTIONS  FOR  NON-CONDENSING  AND  CONDENSING 
COMPOUND  ENGINES — Two  CYLINDERS. 


STEAM. 

NON-CONDENSING  COM- 
POUND  ENGINES. 

CONDENSING  COMPOUND  ENGINES. 

150  pounds. 

125  pounds. 

150  pounds. 

125  pounds. 

100  pounds. 

Small  engines 

1  to  3.  71 
1  to  3.  64 

1  to  3.20 
1  to  3.  06 

1  to  4.  30 
1  to  4.  00 

1  to  3.71 
1  to  3.64 

1  to  3.10 
1  to  3.  06 

Large  engines  

An  example  of  the  tandem  compound  high-speed  engine  is  illus- 
trated in  Fig.  277,  and  represents  a  vertical  section  of  the  Harrisburg 
four-valve  type  with  Corliss  valves.  The  steam-valves  are  controlled 


FIG.  277. — Harrisburg  tandem  compound  engine. 

by  a  fly-wheel  governor  and  movable  eccentric,  while  the  exhaust- 
valves  receive  their  motion  from  a  fixed  eccentric,  which  admits  of  a 
variable  cut-off  and  positive  exhaust-opening. 


COMPOUND  ENGINES 


295 


In  Fig.  278  is  shown  a  section  of  the  cylinders  and  piston-valve 
of  the  Vauclain  compound  engine  for  locomotive  service.  A  high- 
pressure  and  a  low-pressure  cylinder  in  a  single  casting  are  used  on 
each  side  of  the  locomotive;  the  pistons  are  connected  to  a  common 
cross-head,  while  a  single  piston-valve  controls  the  events  for  both 
cylinders. 

The  action  of  the  steam  in  this  system  is  as.  follows:  Steam  is 
admitted  outside  of  the  piston-valve  A,  and,  when  the  valve  is  moved 
to  the  right,  enters  the  left  end 
of  the  high-pressure  cylinder. 
This  action  allows  steam  to 
exhaust  from  the  right-hand 
end  of  the  high-pressure  cylin- 
der through  the  hollow  space  B, 
in  the  centre  of  the  valve  A,  to 
the  left-hand  side  of  the  low- 
pressure  piston,  while  steam  on 
the  right  escapes  through  the 
exhaust-cavities  C,  C  around 
the  valve.  At  the  proper  time 
steam  is  cut  off  from  the  high- 
pressure  cylinder  and  expan- 
sion takes  place.  This  is  fol- 
lowed by  the  closing  of  the 
exhaust  on  the  other  end  of  the 

high-pressure  cylinder,  which  cuts  off  the  steam  in  the  left  end  of  the 
low-pressure  cylinder,  and  hence  expansion  occurs  here  also,  while 
compression  takes  place  in  the  right-hand  end  of  the  high-pressure 
cylinder.  A  star  ting- valve  is  used,  connecting  to  both  ends  of  the 
high-pressure  cylinder,  and  opening  to  the  low-pressure  cylinder  for 
starting. 

A  later  design  of  the  Vauclain  type  is  a  balanced  engine  in  which 
the  motions  of  the  high-  and  low-pressure  pistons  and  connections 
are  in  opposite  directions,  as  shown  in  Fig.  279.  The  cylinders  are  a 
development  of  the  original  Vauclain  four-cylinder  compound  type, 
with  one  piston  slide-valve  common  to  each  pair.  Instead  of  being 
superimposed  and  located  outside  of  the  locomotive-frames,  the  cylin- 
ders are  placed  horizontally  in  line  with  one  another,  the  low-pressure 


FIG.  278. ^-Vauclain  compound  cylinders; 


296 


COMPOUND  ENGINES 


outside  and  the  high-pressure  inside  the  frames.  The  slide-valves 
are  of  the  piston  type,  placed  above  and  between  the  two  cylinders 
which  they  are  arranged  to  control.  A  separate  set  of  guides  and 
connections  is  required  for  each  cylinder.  The  two  high-pressure 
cylinders  being  placed  inside  the  frames,  the  pistons  are  necessarily 
coupled  to  a  crank-axle.  The  low-pressure  pistons  are  coupled 

to  crank-pins  on  the  outside 
of  the  driving-wheels.  The 
cranks  on  the  axle  are  set  at 
90  degrees  with  each  other, 
and  at  180  degrees  with  the 
corresponding  crank-pins  in 
the  wheels.  The  pistons, 
therefore,  travel  in  the  oppo- 
site direction ;  and  the  recipro- 
cating parts  act  against  and 
balance  one  another  to  the 
extent  of  their  corresponding 
weight. 

The  distribution  of  steam 
is  shown  in  the  diagram  (Fig. 
279).  The  live-steam  port  in 
this  design  is  centrally  located 
between  the  induction  ports 
of  the  high-pressure  cylin- 
der. Steam  enters  the  high- 

FIG.  279. — Balanced  compound  cylinder. 

Vauclain.  pressure  cylinder  through  the 

steam-port  and  the  central  ex- 
ternal cavity  in  the  valve.  The  exhaust  from  the  high-pressure  cylinder 
takes  place  through  the  opposite  steam-port  to  the  interior  of  the  valve, 
which  acts  as  a  receiver.  The  outer  edges  of  the  valves  control  the 
admission  of  steam  to  the  low-pressure  cylinder.  The  steam  passes 
from  the  front  of  the  high-pressure  cylinder,  through  the  valve,  to 
the  front  of  the  low-pressure  cylinder,  or  from  the  back  of  the  high- 
pressure  to  the  back  of  the  low-pressure  cylinder.  The  exhaust  from 
the  low-pressure  cylinder  takes  place  through  the  external  cavities 
under  the  front  and  back  portions  of  the  valve,  which  communicates 
with  the  final  exhaust-port.  The  starting-valve  connects  the  two 


COMPOUND  ENGINES 


297 


live-steam  ports  of  the  high-pressure  cylinder,  to  allow  the  steam  to 
pass  over  the  piston. 

In  Fig.  280  are  shown  a  vertical  section  and  a  cross-section  of  a 
convertible  compound  engine,  the  Flinn  type  for  steam-automobiles 
and  -trucks.  Steam  enters  at  the  centre  of  the  high-pressure  steam- 
valve,  and  when  the  intercepting  valve  is  in  the  position  shown  in  the 
left  cross-section,  it  can  pass  from  the  high-pressure  chest  directly 
to  the  low-pressure  chest,  allowing  both  cylinders  to  run  with  high- 
pressure  steam,  the  high-pressure  exhausting  at  A  into  the  main 
exhaust-chest.  This  gives  great  starting  or  climbing  power  to  the 
vehicle.  Otherwise  the  intercepting  valve  is  turned  to  the  position 
shown  in  the  right-hand  lower  section,  closing  the  free  exhaust  from 
the  high-pressure  cylinder  and  the  live-pressure  connection  to  the  low- 
pressure  steam-chest  (compelling  the  exhaust  of  the  high-pressure  cylin- 
der to  enter  the  receiver)  and  to  the  low-pressure  valve. 


FIG.  280. — Convertible  compound  engine. 

A  non-condensing  compound  engine  with  contiguous  cylinders 
and  pistons  connected  to  a  common  cross-head  is  shown  in  Figs.  281 
and  282 — the  product  of  the  American  Engine  Company.  It  is  a  high- 
speed engine  in  which  simplicity  and  compactness  have  been  realized 
to  a  high  degree.  The  valves  are  of  the  duplex-piston  type  on  a 
single  rod,  and  are  operated  from  an  outside  crank-pin  and  centrifugal 
governor  on  the  outside  of  the  fly-wheel,  which  method  makes  an 
automatic  adjustment  simultaneously  for  both  valves. 


298 


COMPOUND   ENGINES 


The  arrangement  of  pistons  and  cross-head  will  be  understood  by 
reference  to  Fig.  282.  The  cross-head  here  shown  is  designed  with 
a  view  to  securing  the  greatest  strength  and  rigidity  with  the  least 


FIG.  281. — Elevation — duplex  compound  engine. 

weight.  The  length  is  made  equal  to  about  twice  the  length  of  stroke 
of  the  engine,  so  that  its  smoothness  of  running  is  quite  independent 
of  any  unequal  division  of  work  between  the  pistons,  if  such  should 
occur;  but  because  of  the  simultaneous  cut-offs  in  both  cylinders  the 


FIG.  282. — Vertical  section — duplex  compound  engine. 

work  is  divided  almost  exactly  between  the  two  pistons  at  all  stages 

of  load,  from  the  simple  friction  load  to  the  fullest  overload  capacity. 

A  feature  of  this  construction  which  appeals  to  the  engineer  in 


COMPOUND  ENGINES 


299 


comparing  it  with  the  tandem  compound  is  the  fact  that  both  pistons 
are  as  accessible  as  with  the  simple  engine. 

The  indicator-diagrams  (Fig.  283),  taken  from  a  nominally  80 
horse-power  engine  with  cylinders  9JX  15x11,  at  275  revolutions, 
100  pounds  pressure,  show  remarkable  uniformity  in  the  division  of 
work  at  greatly  varying  loads,  which  was  38  horse-power  for  the  upper 
card  and  85  horse-power  for  the  lower 
card.  Practically  the  same  proportions 
are  shown  by  the  cards  of  the  larger 
condensing-engine  of  the  same  type. 

A  single-acting  vertical  cross-com- 
pound engine  with  cranks  at  180  degrees 
and  in  which  a  single  piston-valve  set 
crosswise  on  the  heads  of  the  contiguous 
cylinders  controls  the  steam-distribu- 
tion, is  shown  in  the  longitudinal  and 
cross  sections,  Fig.  284.  It  is  a  novel 
and  very  compact  high-speed  motor  for 
all  purposes,  and  is  especially  suited  for 
direct  connection  to  electric  generators. 

The  steam-chest  is  a  separate  casting 
bolted  to  the  cylinder-heads,  and  con- 
tains the  steam-passages  and  the  trans- 
fer-passage from  the  high-  to  the  low- 
pressure  cylinder.  The  pistons  are  of 
the  trunk  type,  the  low-pressure  cylinder 
having  an  inserted  trunk-bearing  sleeve 
that  encloses  cushion-spaces,  Y,  Y  of  air- 
or  steam-leakage,  which  is  drained  by 
the  pipe  and  valve  at  g.  The  sleeve  in 
the  low-pressure  trunk  being  of  e.qual 

area  with  the  high-pressure  trunk,  it  serves  to  prevent  unequal  pressure 
in  the  base  A  and  discharge  at  the  overflow  W  and  at  the  air-  or 
steam-vent  Z.  The  spool  piston-valve  H  travels  in  a  multiported 
liner  which  gives  ample  port-opening  for  high  speed.  The  steam- 
chest  P  and  the  exhaust-chest  T  completely  surround  the  liner.  The 
passage  X  is  a  by-pass  to  the  neck  of  the  spool-valve  for  admitting 
steam  to  the  low-pressure  cylinder  in  starting,  the  liner  having  a  set 


FIG.  283. — Indicator-diagrams. 


COMPOUND  ENGINES  301 

of  ports  to  meet  this  purpose;  d  is  a  relief -valve  for  each  cylinder. 
The  centrifugal  governor  is  enclosed  in  the  fly-wheel  at  F. 

In  Fig.  285  is  a  combined  diagram  of  the  distribution  of  steam- 
pressure  in  the  Westinghouse  vertical  compound  engine,  taken  on  the 
same  card  at  90  pounds  boiler-pressure.  The  same  would  be  obtained 
if  they  were  taken  with  different  indicators,  but  with  the  same  num- 
ber of  spring.  The  cut-off  point  is  c  in  the  high-pressure  cylinder,  and 
exhaust  begins  at  e,  but  as  there  is  only  the  small  steam-chest  of  the 
low-pressure  cylinder  to  exhaust  into,  the  line  eh  is  not  steep.  At  h 
the  low-pressure  valve  opens  the  port  to  that  cylinder,  and  we  get  the 
steam  rapidly  exhausting  from  the  high  pressure  to  the  low.  This  is 


FIG.  285. — Diagram  from  the  Westinghouse  single-acting  compound  engine. 

shown  by  the  drop  below  h  and  the  rise  above  i.  The  two  pencils 
arrive  at  h  and  i  simultaneously.  The  vertical  line  above  i  would 
meet  that  below  h  but  for  the  resistance  offered  by  the  ports  to  the 
passage  of  steam  from  one  cylinder  to  the  other.  From  h  to  b  steam 
is  continually  passing  out  of  the  high-pressure  cylinder  into  the  low, 
the  corresponding  points  in  the  latter  diagram  being  i  and  d.  The 
cause  of  the  fall  toward  d  is  due  to  the  space  occupied  by  the  steam 
in  the  low-pressure  cylinder,  combined  with  that  in  the  high-pressure 
cylinder  together  growing  larger,  and  consequently  the  pressure  must 
grow  less.  At  b  the  exhaust-port  in  the  high-pressure  cylinder  closes, 
and  compression  begins.  Further,  as  no  more  steam  is  coming  from 
the  high-pressure  cylinder,  the  steam  in  the  low  begins  a  slightly 
different  expansion-line,  dn,  until  at  n  exhaust  begins.  Compression 
begins  at  a  and  ends  at  i,  where  admission  commences. 

In  Fig.  286  is  given  a  diagram  of  a  test  made  to  determine  the 


302 


COMPOUND  ENGINES 


steam-consumption  and  the  mechanical  efficiency  and  regulation  of  a 
Buffalo  12  and  18  X  10-inch  horizontal,  tandem-compound,  high-speed, 
non-condensing  engine;  steam-pressure,  125  pounds.  In  this  engine 
the  high-pressure  valve  takes  steam  on  the  inside,  and  exhausts  around 
the  ends.  The  steam  then  passes  through  the  cast  port  in  the  bottom 
of  the  high-pressure  cylinder  to  a  receiver-pipe  on  the  opposite  side, 
and  then  to  the  low-pressure  valve-chest.  The  steam  is  led  to  an 


100 


40 


20 


0   10   20  30  40  50  60  70   80  90  100  110  120  130  140 

Horsepower 

FIG.  286. — -Diagram  of  steam-consumption  and  efficiency. 

exhaust-outlet  at  the  bottom  of  the  low-pressure  valve-chest.  The 
high-pressure  valve  is  a  piston,  while  the  low-pressure  vaive  is  a  slide, 
with  a  balance-plate  on  the  back.  The  two  valves  are  moved  by 
independent  eccentrics  and  rods,  the  two  eccentrics  being  on  opposite 
sides  of  the  engine. 

Governing  is  obtained  entirely  at  the  high-pressure  valve,  the 
motion  of  this  valve  being  controlled  by  a  centrifugal  or  shaft  governor. 
The  engine  was  set  to  run  at  about  285  revolutions. 

The  diagram  shows  curves  of  the  steam-consumption  for  non- 
condensing  tests  and  the  mechanical  efficiency.  Steam-consumption 
is  figured  for  dry  steam,  the  steam  being  at  no  time  over  4  per  cent, 
moisture  in  the  main  and  usually  less  than  3  per  cent.  Curve  A 
shows  the  relation  between  developed  horse-power  and  steam  per 
developed  horse-power  hour,  curve  B  between  indicated  horse-power 
and  steam  per  indicated  horse-power  hour,  and  curve  C  between  de- 
veloped horse-power  and  mechanical  efficiency. 


COMPOUND  ENGINES 


303 


In  Fig.  287  is  given  a  diagram  showing  the  efficiency  and  steam- 
consumption  in  a  test  of  a  Reeves  vertical  cross-compound  non-con- 
densing engine,  12  and  20  X  14  inches,  and  a  condensing-engine 
10  J  and  20  X  14;  it  shows  the  difference  in  efficiency  and  steam- 
consumption  under  like  conditions  of  steam-pressure  and  valve-gear. 
The  ratio  of  cylinder-volume  for  the  condensing  trial  was  1  to  3.6, 
vacuum  24-inch,  and  for  the  non-condensing  trial  1  to  2.75,  and  nor- 
mally 160  horse-power. 

In  this  test  the  power  was  measured  by  the  use  of  a  Prony  brake, 
and  the  steam-consumption  and  efficiency,  over  a  considerable  range 


ioo 

ii  95 


85 

I  80 
575 
^  36 
I  34 
a;  32 


28 

|  26 
in  24 

Q  22 
°20 


\\ 


\\ 


\\ 


20 


40        60        80        100       120       140       160       180       200 
Horsepower 


FIG.   287. — Comparative  diagram  of  efficiency  and  steam-consumption  in 
non-condensing  and  condensing  engines. 

of  load,  are  easily  seen  from  the  curves.  Two  things  may  be  noticed, 
however:  The  cut-off,  even  at  the  higher  loads,  does  not  seem  to  be 
late  enough  to  cause  any  marked  rise  in  the  steam-consumption;  and 
the  mechanical-efficiency  curves  show  a  steady  increase  with  the  load 
at  any  given  steam-pressure,  and  the  efficiency  falls  off  but  slightly 
on  overload. 


304 


COMPOUND  ENGINES 


RECEIVERS 

A  receiver  is  not  essential  to  a  compound  tandem  engine  with 
immediate  connections  between  the  cylinders,  although  the  usual 
pipe-connections  operate  in  a  small  measure  as  a  receiver.  With 
cross-compound  engines  with  cranks  at  90  degrees,  the  receiver 
modifies  the  steam-expansion  to  a  considerable  extent. 

The  distribution  of  the  steam  in  the  cylinders  of  a  tandem  com- 
pound engine,  at  various  points  of  the  stroke,  is  graphically  shown 
in  the  diagram  (Fig.  288),  neglecting  clearance-  and  steam-passages. 
In  the  diagram  ab  =  volume  of  the  high-pressure  cylinder;  ac  =  volume 
of  low-pressure  cylinder  =  1  to  4;  the  vertical  line  ad  =  initial  pressure; 
exhaust  of  high  pressure  is  at  f,  one-third  cut-off;  initial  pressure  of 
low-pressure  cylinder  =  ag  =  terminal  pressure  of  the  high-pressure 
cylinder  and  takes  steam  to  the  end  of  the  stroke;  the  curve  gmk 
represents  the  fall  of  pressure  in  the  low-pressure  cylinder,  and  the 
curve  fnh  represents  the  decreasing  back  pressure  in  the  high-pressure 


d  e 


a      p      b 
FIG.  288. — Diagram,  without  receiver,  of  tandem  compound  engine. 

cylinder  (each  shaded  section  representing  the  theoretical  indicator- 
diagram  for  its  steam-pressure);  pn  =  rm,  and  ck  =  ah. 

In  Fig.  289  is  a  diagram  of  the  distribution  of  steam  as  well 
as  the  theoretical  indicator-card  for  each  cylinder,  representing  the 
shaded  part.  Volume  of  cylinders,  1  to  3;  cut-off,  one-half  in  each 
cylinder.  Then,  if  the  steam  be  admitted  to  the  high-pressure  cylinder 
for  one-half  the  stroke,  de  =  J  ab  is  the  line  of  admission,  e  is  the  point 
of  cut-off,  and  ef  the  curve  of  expansion  to  the  end  of  the  stroke  of  the 


COMPOUND   ENGINES 


305 


high-pressure  cylinder,  the  terminal  pressure  being  bf  =  J  ad.  Com- 
munication is  now  opened  with  the  receiver,  and  the  pressure  falls  to 
g,  the  pressure  bg  depending  on  the  volume  of  the  receiver  and  on  the 
pressure  of  the  steam  in  it.  But  there  is  as  yet  no  admission  to  the 
low-pressure  cylinder  till  another  half-stroke  has  been  made.  The 
diagram  of  work  done  by  the  high-pressure  piston  will  therefore  show 
an  increasing  back-pressure  curve,  gt,  as  that  piston  returns,  till  it 


r  a       s        b 

FIG.  289. — Diagram  with  receiver  and  condenser. 

reaches  half-stroke,  when  the  low-pressure  steam-port  opens  and 
admits  steam  at  the  initial  pressure  ah  =  st.  The  pressure  now  falls 
by  expansion  of  the  steam  behind  the  low-pressure  piston,  the  terminal 
pressure  an  in  the  high-pressure  cylinder  being  equal  to  the  pressure 
rm  in  the  low-pressure  cylinder  at  half-stroke.  Cut-off  now  takes  place 
in  the  low-pressure  cylinder,  and  the  steam  expands  behind  the  piston 
to  ck  =  J  ad  =  J  bf,  at  which  point  it  escapes  to  the  condenser,  when 
the  pressure  falls  to  the  line  of  back  pressure. 

The  volume  of  a  receiver  is  relative  to  the  volume  of  the  high- 
pressure  cylinder  for  the  best  distribution  of  the  steam,  and  for  two 
expansions  it  should  be  five  times  the  volume  of  the  high-pressure 
cylinder.  For  triple  expansion  the  first  receiver  should  be  six  times 
the  volume  of  the  high-pressure  cylinder;  for  the  second  receiver  its 
volume  should  be  four  times  the  volume  of  the  intermediate  cylinder. 
The  variation  in  the  receiver-pressure  will  be  greater  for  a  small 
receiver  than  for  a  large  one,  and  also  depend  upon  the  initial  pressure 
for  any  proportional  size. 

As  an  illustration  of  the  line  of  pressure  in  the  receiver  of  a  cross- 


306 


COMPOUND  ENGINES 


compound  engine  with  cranks  at  90  degrees  and  cylinder  proportions 
1  to  4,  the  diagram  (Fig.  290)  represents  the  general  conditions.  In 
the  normal  running  of  the  engine  with  the  cut-off  in  the  high-pressure 
cylinder  at  one-half  and  in  the  low-pressure  cylinder  at  one-fourth 
stroke,  the  pressure  will  increase  in  the  receiver  from  the  opening  of 

the  exhaust  in  the  high-pressure 
cylinder  at  j  until  the  valve  of  the 
low-pressure  cylinder  opens  at  1, 
then  falls  until  the  cut-off  of  the 
low-pressure  cylinder  takes  place 
at  m,  then  rises  until  the  high- 
pressure  stroke  is  completed  at 
n,  and  the  next  exhaust  repeats 
the  pressure-curve  from  j  to  1. 
With  the  cut-off  at  half-stroke  in  each  cylinder,  the  pressure  lines  1m 
and  mn  will  be  extended,  each  to  the  half-length  of  the  stroke. 

In  Fig.  291  are  shown  the  relative  position  of  the  pistons  at  exhaust 
in  the  high-pressure  cylinder  and  cut-off  at  half-stroke  in  the  low- 
pressure  cylinder — when  the  receiver-pressure  is  low,  as  in  the  left- 
hand  figure — and  at  the  moment  of  cut-off  in  the  high-pressure  cylinder 
and  valve-opening  in  the  low-pressure  cylinder,  when  the  receiver- 
pressure  is  high,  as  in  the  right-hand  figure. 


G 

k 
_^   ... 

B 

^^ 

1  

P  — 

1^==; 

\^ 

^=^  fj 

n 

r  -_-  ;.— 

iL-        ..Jn 

FIG.  290. — Diagram  of  receiver-pressure. 


Receiver 


11   • 

•51 

*( 

=  flllllli 

illl 

"It 

b 

= 

.  ;'||||| 

n 

b 

s p       Receiver 

\          a 


FIG.  291. — Diagram  of  pressures  in  receiver,  variable. 

The  economy  of  reheating  the  steam  in  the  receiver  has  not  been 
satisfactorily  defined  by  experiments  made  in  Europe  and  the  United 
States  for  this  purpose.  In  a  series  of  trials  in  England  for  reheating 
the  steam  within  the  receiver  by  a  copper  helical  coil,  negative  results 
were  obtained  in  nine-tenths  of  the  trial  runs.  The  conclusions 


COMPOUND  ENGINES  307 

arrived  at  by  these  trials  were  that  the  influence  of  the  reheater  was 
as  follows: 

(a)  Reducing  the  amount  of  condensation  in  the  receiver. 

(b)  Raising  the  receiver-pressure. 

(c)  Raising  the  mean  pressure  throughout  the  engines. 

(d)  Increasing  the  speed  of  revolution  of  the  engines. 

(e)  Increasing  the  dryness  of  the  steam  acting  in  the  low-pressure 
cylinder. 

These  may  be  ranked  as  effects  which  are  in  themselves  favorable 
to  economy. 

The  influence  of  the  reheater  was  found,  however,  equally  marked 
in  effects  which  were  detrimental  to  economy,  namely: 

(a)  Lowering  the  mechanical  efficiency  of  the  engine. 

(b)  Increasing  the  steam-consumption  per  horse-power  developed. 
Experimental  tests  in  the  United  States  have  added  no  positive 

economical  results  by  reheating,  over  a  thorough  felting  of  the  receiver 
and  connecting-pipes. 

The  use  of  superheated  steam  now  coming  into  consideration  and 
practice  for  all  conditions  of  expansion,  is  of  such  importance  in  the 
economy  of  multicylinder  engines  for  both  land  and  marine  service, 
that  reheating  in  receivers  will  no  doubt  be  left  in  its  experimental 
stage  in  deference  to  the  better  economy  of  superheat. 


CHAPTER    XVIII 


TRIPLE-   AND    QUADRUPLE-EXPANSION    ENGINES 

THE  increased  efficiency  due  to  a  greater  range  of  expansion  in  the 
triple  and  quadruple  effect  from  high  pressures  has  brought  steam- 
power  to  its  highest  degree  of  usefulness  and  economy.  It  is  but 
a  few  years  since,  in  the  memory  of  old  engineers,  that  a  10-per-cent. 
thermal  efficiency  was  good  practice;  but  improvements  in  metallurgy 
and  the  mechanic  arts — which  have  made  possible  great  advances  in 
steam-pressure  and  its  multiple  expansion — together  with  the  progres- 
sive experience  in  design,  have  more  than  doubled  the  power-economy 
of  former  years  and  brought  the  thermal  efficiency  up  to  23  per  cent, 
and  the  mechanical  efficiency  to  95  per  cent.,  and  possibly  more.  It 
is  claimed  that  less  than  1  pound  of  coal  per  indicated  horse-power 
per  hour  has  been  obtained  in  test  trials. 

The  amount  of  steam  or  its  equivalent  per  indicated  horse-power 
per  hour  varies  with  the  pressure  and  cut-off  at  the  higher  pressures 
now  in  use;  and  its  distribution  in  triple-expansion  engines  is  shown 
approximately  in  the  following  table : 

TABLE  XXXVIII. — WATER-CONSUMPTION  IN  TRIPLE-EXPANSION  ENGINES. 


INITIAL  PRESSURE  BY  GAUGE. 

MEAN  EFFECTIVE  PRESSURE,  OR 
ABOVE  VACUUM. 

Cut-off, 
per  cent. 

High-pres- 
sure cylin- 
der, 

Interme- 
diate-pres- 
sure cylin- 

Low-pres- 
sure cylin- 
der, 

High-pres- 
sure cylin- 
der, 

Interme- 
diate-pres- 
sure cylin- 

Low-pres- 
sure cylin- 
der, 

Feed-water 
per  I.  H.  -P. 
per  hour, 
pounds. 

pounds. 

pounds. 

pounds. 

pounds. 

pounds. 

pounds. 

( 

120 

37.8 

1.3 

38.5 

17.1 

6.5 

12.05 

30    ] 

140 

43.8 

2.8 

46.5 

18.6 

7.1 

11.4 

( 

160 

49.3 

3.8 

55.0 

20.0 

8.0 

10.75 

( 

120 

38.8 

2.8 

51.5 

22.8 

8.6 

11.65 

40    \ 

140 

45.8 

3.9 

59.5 

23.7 

9.1 

11.4 

( 

160 

51.3 

5.3 

70.5 

25.5 

10.0 

10.85 

( 

120 

39.8 

3.7 

60.5 

26.7 

10.1 

12.2 

50    \ 

140 

46.8 

4.8 

70.5 

28.0 

10.8 

11.6 

I 

160 

52.8 

6.3 

82.5 

30.0 

11.8 

11.15 

308 


TRIPLE-   AND  QUADRUPLE-EXPANSION  ENGINES         309 

The  record  of  a  test  of  a  high-duty  triple-expansion  pumping- 
engine  of  the  Allis-Chalmers  vertical  type,  lately  erected  at  the  St. 
Louis  water-works,  is  worthy  of  reference  for  its  showing  of  thermal 
and  mechanical  efficiency. 

RESULTS    OF    DUTY    TEST. 

Duration  of  test 24  hours. 

Diameter  of  cylinders 34  inches,  62lnches,  and  94  inches. 

Stroke  of  engine 72 

Diameter  of  plungers 33f     " 

Average  steam-pressure  at  engine 140 . 24  pounds. 

Average  first  receiver-pressure 26.36       " 

Average  second  receiver-pressure 2 .77       " 

Average  vacuum-pressure  by  cards 13.21       " 

Average  barometer-pressure 14.46       " 

Average  net  head  pumped  against 238.2323  feet. 

Average  revolutions  per  minute 16.539 

Piston-speed  per  minute 198 .44  feet. 

Total  water  pumped 20,070,690  gallons. 

Total  water  received  from  engine 220,129  pounds. 

Average  moisture  in  steam 0. 13  per  cent. 

Indicated  horse-power 865.23  horse-power. 

Delivered  horse-power 842.69      "          " 

Per  cent,  friction 2.60  per  cent. 

Average  moist  steam  per  indicated  horse-power 

per  hour 10.60  pounds. 

Average  dry  steam  per  indicated  horse-power 

per  hour 10.59       " 

Average    British   thermal  units  per  indicated 

horse-power  per  minute 201 .39  British  thermal  units. 

Mechanical  efficiency 97 .4  per  cent. 

Duty  per  1,000  pounds  of  steam 181,068,605  foot-pounds. 

Duty  per  1,000,000  British  thermal  units 158,851,000     " 

Thermal  efficiency 21 .06  per  cent. 

As  the  multicompounding  of  steam-expansion  enables  the  fullest . 
advantage  to  be  taken  of  the  expansion  from  the  highest  pressures 
available — by  reducing  the  range  of  temperature  in  any  one  cylinder 
and  its  initial  condensation,  and  by  utilizing  its  reevaporation  in  a 
succeeding  cylinder — as  also  the  economy  due  to  the  greater  total 
range  of  temperatures  with  the  lesser  extreme  strains  in  the  mechan- 
isms— this  system  of  steam-power  has  been  brought  to  apparently 
the  highest  degree  of  perfection  possible. 

In  the  diagram  (Fig.  292)  are  shown  the  approximate  divisions 
in  a  triple-expansion  engine  as  between  temperatures  and  absolute 


310         TRIPLE-  AND  QUADRUPLE-EXPANSION  ENGINES 


pressures  from  an  initial  pressure  of  150  pounds  absolute.  These 
proportions  may  be  varied  to  suit  the  equalized  total  pressure  in  each 
cylinder  for  any  initial  pressure  proposed. 


150  IbS. 


To  Condenser 


FIG.  292. — Pressures  and  temperatures  in  triple  expansion. 

The  cylinder  disposition  and  proportions  in  triple-  and  quadruple- 
expansion  engines  vary  in  a  considerable  degree,  and  are  illustrated 
in  the  following  figures: 

A  high-pressure,  intermediate-pressure,  and  low-pressure  cylinder 
in  line  with  a  three-crank  shaft,  with  cranks  at  120  degrees  (Fig.  293). 

A  high-pressure,  inter- 
mediate-pressure, and  two 
low-pressure  cylinders  on  a 
four-crank  shaft  at  90  de- 
grees, or  alternating  at  180 
degrees  (Fig.  294). 

A  quadruple  -  expansion 
engine  with  a  high-pressure, 
consecutive  first  and  second 
intermediate  -  pressure,  and 
one  low  -  pressure  cylinder 
(Fig.  295).  The  quadruple 
is  also  built  on  the  tandem 
model,  with  high  and  first 
intermediate  tandem  vertical  and  second  intermediate  and  low  tan- 
dem vertical  in  the  marine  service. 

The  relative  cylinder-volumes  in  these  engines  for  high  initial 


FIG.  293. — Triple  expansion. 


To  Condenser 

FIG.  294. — Four-cylinder  triple  expansion. 


TRIPLE-  AND  QUADRUPLE-EXPANSION  ENGINES         311 


pressure  are  from  2.3  to  2.7,  and  are  divided  so  as  to  give  about  20 
as  the  total  number  of  expansions  in  a  quadruple-expansion  engine. 


To  Condenser 


UP.    CYLINDER 
LOOKING   AFT 


FIG.  295. — Four-cylinder  quadruple  expansion. 

The  relative  cylinder-volumes  in  some  recently  designed  triple- 
expansion  marine  engines  of  over  5,000  horse-power  to  each  engine, 
arranged  for  one  high-pressure, 
one  intermediate  -  pressure,  and 
two  low-pressure  cylinders,  are 
as  1:2.7:2.6  volumes.  The  latest 
practice,  as  shown  in  the  designs 
of  the  United  States  Bureau  of 
Steam  -  Engineering  for  the  en- 
gines of  the  North  Carolina  and 
Montana,  has  proportions  of  cylin- 
der-volumes of  1:2.64:2.71,  with 
one  high-pressure,  one  interme- 
diate-pressure, and  two  low-pres- 
sure cylinders  in  triple-expansion 
engines,  and  with  piston-valves  for 
all  the  cylinders,  there  being  one 
piston-valve  for  the  high-pressure 
cylinder  and  two  each  for  the 
others. 

The  illustrated  details  of  these 
engines  are  shown  in  Figs.  296,  297, 
and  298,  and  represent  results  of 
design  from  the  latest  ideas  for 
compactness  and  large  power  for  FlQ  296._End  view  of  triple-expan- 
war-ships  which  consist  of  two  en-  Sion  engine.  U.  S  Navy. 


314         TRIPLE-  AND  QUADRUPLE-EXPANSION   ENGINES 

gines  of  23,000  combined  indicated  horse-power,  and  with  the  following 
details  of  construction: 

Number  of  cylinders One    high-pressure,    one   intermediate-pres- 
sure, two  low-pressure. 

Diameter  of  cylinders 38£  inches,  63J  inches,  74  inches  each. 

Stroke 48        " 

Piston-valves  for  all  cylinders. 

Initial  steam-pressure 250  pounds. 

Boiler-pressure 265       " 

Diameter  of  high-pressure  piston-valve  24 \  inches. 

Diameter  of  each  low-pressure  piston- 
valve  27        " 

Revolutions 120  per  minute. 

All  main  and  valve  cylinders  have  liners.     Piston-clearance  in  all  cylinders  is  f 

inch  at  the  top  and  f  inch  at  the  bottom,  with  a  probable  average  total  clearance  of 

about  2  per  cent. 

The  main  shaft,  crank-pins,  cross-head  pins,  and  piston-rods  are  hollow. 

Cranks  of  high-  and  low-pressure  cylinders,  adjacent,  are  180  degrees;  cranks  of 

intermediate-  and  low-pressure  cylinders,  adjacent,  180  degrees;    cranks  of  each 

pair,  90  degrees. 

A  novel  triple  compound  marine  engine  which  may  be  used  con- 
densing for  a  quadruple  effect,  is  shown  in  front  and  cross  sections 


FIG.  299. — Triple  compound  marine  engine. 

in  the  two-part  Fig.  299.     The  principal  novelty  is  the  three-part 
eccentric  oscillating  upon  the  crank-pin,  and  upon  each  of  which  a 


TRIPLE-  AND  QUADRUPLE-EXPANSION  ENGINES         315 

strap  fixed  to  the  piston-rod  of  each  cylinder  slides  in  ways  parallel 
with  each  piston-rod.  The  throw  of  the  eccentrics  and  that  of  the 
crank  are  each  equal  to  one-half  the  piston-stroke.  The  crank-eccen- 
trics are  set  at  120  degrees,  as  shown  at  a.  The  three-piston  valves  are 
directly  connected  by  rods  to  thin  straps  on  an  angularly  mounted 
cylinder  that  slides  on  the  shaft  by  the  hand-lever  for  forward,  stop, 
or  reverse  motion. 

Piston-valves  are  used,  taking  the  steam  in  the  middle  and  ex- 
hausting at  the  ends.  The  steam  passes  from  the  first  valve,  through 
the  triangular  space  between  the  cylinders,  to  the  next  valve-chest. 


FIG.  300. — Triple-expansion  marine  engine.     Type  of  the  steamer  Minnesota. 

In  Fig.  300  is  shown  a  vertical  section  of  a  triple-expansion  marine 
engine  in  which  the  high-pressure  cylinder  has  a  piston-valve,  while 
the  intermediate-  and  low-pressure  cylinders  have  slide-valves.  Pro- 
portion of  cylinders,  1,  5,  15  in  area;  stroke,  48  inches;  crank  positions, 
120  degrees;  high-pressure  cylinder,  23  inches  diameter;  intermediate 
cylinder,  51  inches  diameter;  low-pressure  cylinder,  89  inches  diameter. 

In  Fig.  301  is  shown  a  vertical  section  of  a  triple-expansion  engine 
with  a  double  tandem  high-pressure  cylinder  in  which  its  pistons  act 
as  valves  to  the  intermediate  cylinder.  The  object  of  this  is  to  produce 


316         TRIPLE-  AND  QUADRUPLE-EXPANSION  ENGINES 

an  arrangement  of  cylinders,  steam-valves,  and  ports  whereby  the 
back  pressure  of  the  intermediate  cylinder  will  not  act  as  an  opposing 
force  on  the  high-pressure  piston,  and  will  also  furnish  full  pressure 
of  steam  in  the  intermediate  without  increasing  back  pressure  in  the 
high.  Steam  enters  the  chamber  a3,  passes  through  an  opening 
between  the  two  piston-valves,  which  open  to  the  upper  piston,  a, 
when  it  passes  the  bottom  centre.  The  cut  shows  it  in  the  act  of 
closing. 

When  working  as  a  triple  expansion  the  valve  closes  when  the 
piston  reaches  the  point  62,  which  allows  the  steam  to  enter  cylinder 


FIG.  301. — Duplex-piston  triple-expansion  engine. 

B  above  piston  b  at  full  pressure,  but  the  crank  to  cylinder  A  is  on  the 
quarter  where  it  moves  at  its  highest  speed,  while  the  piston  b  moves 
down.  It  will  also  be  seen  that  lower  piston  a  reaches  the  top  of  its 
cylinder  at  the  same  time,  but  instead  of  being  in  a  position  to  exhaust 
as  in  the  upper  one,  it  will  be  in  the  position  to  receive  through  lower 
port  a9,  valve  a5  having  moved  down  far  enough  to  open.  The  pistons 
a,  a  start,  on  the  return-stroke,  with  a  reversion  of  valve-movements. 
It  is  a  curious  study  in  steam-pressure  interchange  from  piston  port 
opening. 


CHAPTER    XIX 

THE    STEAM-TURBINE 

THE  steam-turbine,  like  the  reciprocating  engine,  has  a  history 
with  an  inception  much  earlier  than  that  of  steam-expansion,  and 
is  coeval  with  the  knowledge  of  steam  as  a  power  possibility.  The 
Heron  steam-motor  was  a  reaction-turbine  of  which  there  have  been 
several  models  described  in  the  early  accounts.  After  nearly  1,800 
years  since  the  introduction  of  Heron's  eolipile  Branca  brought  out, 
in  1629,  an  impulse-wheel  in  which  a  jet  of  steam  impinged  upon 
the  flat  vanes  of  a  wheel.  The  principle  of  expansion  had  not  yet 
dawned. 

In  the  later  years  of  the  eighteenth  century  the  principles  of 
turbine-action  came  to  an  experimental  stage,  and  Watt,  Ericsson, 
Perkins,  and  others  made  trials  with  steam-turbines  without  per- 
manent results.  Up  to  1901  no  less  than  four  hundred  patents  were 
issued  in  England  on  the  subject  of  steam-turbines.  In  1843  Pilbrow 
patented  a  stage-expansion  steam-turbine,  and  Wilson,  in  1848, 
patented  the  first  radial-flow  turbine,  which  in  design  anticipated 
the  Dow  radial-flow  turbine. 

In  the  United  States  the  reaction-engine  of  William  Avery  had  a 
few  years  of  successful  operation.  Its  rotor  consisted  of  two  hollow 
arms,  thin  and  sharp  like  sword-blades,  mounted  on  a  hollow  axis, 
and  revolving  in  a  dished-disk  chamber.  A  small  orifice,  Jx}  inch, 
opened  on  the  back  of  each  blade,  at  the  extreme  end.  One  of 
its  drawbacks,  as  claimed,  was  the  friction-wear  on  the  blades  in 
cutting  the  exhaust-steam  in  the  chamber. 

The  author's  experience  with  an  Avery  turbine,  erected  in  Buffalo, 
N.  Y.,  in  1833  by  his  father,  showed  that  at  1,000  revolutions  per 
minute  the  stuffing-box  on  the  hollow  shaft  could  not  be  kept  tight 
with  the  method  of  packing  then  in  use,  and  that  the  oil  in  the  journals 
and  stuffing-box  burned  or  baked  by  the  heat  of  the  steam  and  friction, 
and  cut  the  bearings.  Hemp  and  winter-strained  sperm-oil  were  the 

317 


318  THE  STEAM-TURBINE 

best  materials  in  those  days  for  packing  and  lubrication.  The  turbine 
was  soon  replaced  by  a  reciprocating  engine. 

The  Parsons  type  first  took  practical  form  about  1884,  and  the 
De  Laval  type  in  1883,  since  which  time  the  progress  in  design  and  the 
improvement  in  the  machinery  of  construction  have  brought  both 
types  to  their  present  efficiency  and  power. 

In  both  the  De  Laval  and  Parsons  steam-turbines  power  is  gener- 
ated by  the  impact  of  a  jet  of  steam  upon  buckets  on  the  periphery 
of  a  revolving  disk.  The  essential  differences  between  the  two  types 
of  motors  are  these:  The  De  Laval  turbine  has  a  single  disk  with 
several  steam-jets  or  nozles.  The  nozles  have  divergent  apertures 


D 

FIG.  302. — The  Avery  turbine. 

in  which  the  expansion  of  the  steam  takes  place.  The  single  turbine- 
disk  revolves  at  a  high  rate  of  speed,  say  from  10,000  to  30,000  revolu- 
tions per  minute,  according  to  the  size  of  the  motor,  this  speed  being 
reduced  to  about  one-tenth  on  the  main  shaft  by  means  of  accurately 
cut  spiral  gears. 

The  Parsons  type  of  turbine,  on  the  other  hand,  has  a  series  of 
disks  mounted  upon  a  common  shaft  and  alternating  with  parallel 
blades  fixed  within  the  casing  of  the  shaft.  There  are  buckets,  or 
cups,  upon  both  the  revolving  disks  and  the  fixed  blades,  the  fixed 
buckets  being  reversed  in  relation  to  the  moving  cups.  The  steam, 
admitted  first  through  a  set  of  stationary  blades  or  buckets,  impinges 
at  an  angle  upon  the  first  rotating  disk  and  imparts  motion,  passing 
thence  through  another  set  of  fixed  blades  to  the  second  disk  upon 
the  main  shaft,  and  thus  through  the  entire  series  of  alternately 


THE  STEAM-TURBINE  319 

fixed  and  rotating  buckets.  The  area  of  the  passages  increases  progres- 
sively to  correspond  with  the  expansion  of  the  steam  as  it  is  used 
on  the  successive  disks.  The  expansion  of  steam  is  accomplished  in 
the  turbine  instead  of  in  the  nozle,  as  in  the  De  Laval  motor.  The 
buckets  in  a  given  size  of  Parsons  turbine  number  about  3,000,  as 
against  about  350  in  a  De  Laval  motor  of  the  same  size. 

The  efficiency  of  the  steam-turbine  varies  according  to  conditions, 
just  as  the  economy  of  the  reciprocating  engine  is  similarly  affected. 

Friction  is  reduced  to  a  minimum  in  the  steam-turbine,  owing  to 
the  absence  of  sliding  parts  and  the  small  number  of  bearings.  In 
one  type  there  are  practically  but  two  bearings.  The  absence  of 
internal  lubrication  is  also  an  important  consideration,  especially 
when  it  is  desired  to  use  condensers. 

As  there  are  no  reciprocating  parts  in  a  steam-turbine,  and  as  a 
perfect  balance  of  its  rotating  parts  is  absolutely  essential  to  its  suc- 
cessful operation,  vibration  is  reduced  to  such  a  small  element  that 
the  simplest  foundations  will  suffice,  and  it  is  safe  to  locate  steam- 
turbines  on  upper  floors  of  a  factory  if  this  be  desirable  or  necessary. 

The  perfect  balance  of  the  moving  parts  and  the  extreme  simplicity 
of  construction  tend  to  minimize  the  wear  and  increase  the  life  of  a 
turbine  and  at  the  same  time  to  reduce  the  chance  of  interruption  in  its 
operation  through  derangement  or  damage  of  any  of  its  essential  parts. 

Although  hardly  beyond  the  stage  of  its  first  advent  in  the  motive- 
power  field,  the  steam-turbine  has  met  with  much  favor,  and  there  is 
promise  of  its  wide  use  for  the  purposes  to  which  it  is  particularly 
adapted.  At  present,  however,  its  uses  are  restricted  to  service  that 
is  continuous  and  regular,  its  particular  adaptability  being  for  the 
driving  of  electrical  generators,  centrifugal  pumps,  ventilating  fans, 
and  similar  high-speed  work,  especially  where  starting  under  load  is 
not  essential. 

Steam-turbines  are  now  being  built  in  the  United  States  in  all 
sizes  up  to  5,000  horse-power.  Their  use  abroad  covers  a  longer  period 
and  has  become  more  general. 

The  application  of  the  steam-turbine  to  the  propulsion  of  ships 
has  produced  surprising  speed  results.  The  Turbinia,  in  which  the 
first  experiments  were  tried  in  England,  was  a  vessel  100  feet  long, 
9  feet  beam,  3  feet  draught,  and  44  tons  displacement.  As  finally 
equipped  this  vessel  attained  a  speed  of  34J  knots  at  Spithead  in  1897, 


320  THE  STEAM-TURBINE 

with  about  2;300  indicated  horse-power.  The  torpedo-boat  destroyer 
Viper,  subsequently  built  for  the  British  Admiralty,  was  210  feet  long, 
21  feet  beam,  and  350  tons  displacement,  and  a  speed  of  36.858  knots 
was  developed. 

The  arrangement  of  nozles  and  buckets  in  the  De  Laval  type  of 
turbines  has  been  made  with  nozles  impinging  on  buckets  across  the 
periphery  of  the  wheel,  as  shown  in  Fig.  303.  The  nozles  are  of  the 


FIG.  303. — Peripheral  bucket-turbine. 

expanding  type,  as  shown  in  Fig.  123,  from  which  the  jets  of  steam 
impinge  on  the  edge  of  curved  buckets  of  the  Pelton  type  and  dis- 
charge at  the  sides  into  the  surrounding  chamber.  The  long,  slender 
shaft  shown  in  the  cross-section  is  to  take  up  the  unbalanced  vibration 
of  the  disk.  This  model  has  not  been  credited  with  economical  success. 

The  side-nozle  turbine,  with  a  number  of  nozles  impinging  upon 
the  side  at  an  angle  of  from  15  to  20  degrees  against  lunette  buckets, 
and  exhausting  at  the  other  side  to  the  atmosphere  or  to  a  condenser, 
is  the  De  Laval  type  (Fig.  304). 

The  wheel  shown  in  Fig.  305  consists  of  a  steel  disk  carefully 
balanced,  and  in  form  is  very  thick  at  the  centre  and  made  thinner 
as  the  outer  edge  is  approached,  a  rim  being  formed  at  the  edge,  in 
which  the  buckets  are  mounted.  A  hub  is  formed  on  either  side  at 
the  centre,  in  which  is  mounted  the  shaft,  as  shown.  The  shaft  is 
formed  of  two  separate  pieces  in  the  larger  sizes,  this  form  and  method 
of  mounting  having  proved  to  be  the  most  flexible.  The  buckets 
are  separate  forgings  of  steel,  held  in  the  wheel  by  a  bulb-shank 
fitting  into  a  corresponding  slot  milled  in  the  wheel. 

This  shank  is  made  a  driving-fit,  which  serves  to  hold  the  buckets 


THE  STEAM-TURBINE 


321 


in  place.  The  surface  of  these  buckets  against  which  the  steam  issues 
is  not  finished,  but  retains  the  hardened  scale  formed  by  forging, 
presenting  a  most  excellent  wearing  surface.  In  case  renewals  are 
necessary,  they  can  be  made  at  small  expense  and  in  a  very  short 
time.  The  nozles  are  made  of  bronze,  and  so  designed  for  the  different 
steam-pressures  and  vacuums  that  they  permit  the  free  expansion  of 
the  steam.  When  properly  proportioned  for  a  giv-en  initial  and  ter- 
minal pressure,  the  steam  as  it  leaves  the  ends  of  the  nozles  assumes 
a  parallel  form  of  jet,  and  for  this  reason  it  is  not  found  necessary 
to  place  the  nozles  close  to  the  buckets,  the  loss  through  dissipation 
of  energy  between  them  being  so  small  that  it  can  be  ignored.  The 
amount  of  divergence  in  the  nozle  varies  considerably  for  different 
initial  and  terminal  pressures.  As  the  nozles  do  not  really  confine 
the  steam,  but  simply  prevent  outside  influences  from  affecting  the 
free  expansion,  there  is  no  wear  on  them,  and  they  last  for  years. 
As  the  steam  is  expanded  in  these  nozles  to  the  exhaust-pressure 


Turbine  Wheel 


FIG.  304. — Side-nozle  De 
Laval  turbine. 


FIG.  305. — Section  of  De  Laval  turbine. 


under  which  the  turbine  operates  and  before  coming  in  contact  with 
the  wheel,  the  pressure  on  both  sides  is  the  same,  thereby  preventing 
any  end-thrust,  and  the  acting  and  reacting  forces  of  the  steam  as  it 
strikes  and  leaves  the  vanes  of  the  wheel  are  substantially  the  same, 
owing  to  the  shape  of  the  buckets  and  the  angle  at  which  the  steam 
strikes  them. 

The  turbine-wheel  revolves  on  its  own  centre  of  gravity  by  means 
of  the  flexible  shaft  mounted  on  bearings,  and  the  floating  bearings 


322 


THE  STEAM-TURBINE 


are  really  metallic  packing,  preventing  the  leakage  of  exhaust-steam 
when  running  non-condensing,  and  the  entrance  of  air  into  the  exhaust- 
chamber  when  operated  condensing.  The  steam,  after  passing  through 
the  wheel,  goes  direct  to  the  exhaust-pipe  in  the  exhaust-chamber, 
the  space  on  either  side  of  the  wheel  being  in  free  communication 
with  this  exhaust-chamber.  As  the  rotative  speed  of  the  turbine- 
wheel  is  high  it  is  necessary  to  have  some  means  of  reduction  in  order 
to  apply  it  at  low  speeds,  and  this  is  accomplished  by  means  of  double 
spiral  gears  of  small  pitch. 

The  system  of  governing  consists  of  a  balanced  double-beat  poppet- 
valve,  con  trolled. by  a  governor  of  extremely  simple  design  and  of  the 
centrifugal  type. 

The  steam  in  this  type  of  turbine  performs  its  work  by  utilizing 
the  velocity-energy  of  the  steam  by  expanding  it  before  reaching  the 

moving  or  working  part 
of  the  machine.  This 
is  done  through  the 
agency  of  nozles  of  defi- 
nite design,  so  placed  as 
to  direct  the  steam,  af- 
ter it  has  been  expand- 
ed, against  the  vanes 
or  buckets  of  a  wheel 
mounted  on  a  flexible 
shaft  with  which  it  ro- 
tates. With  these  features  understood  the  simplicity  and  power  of 
the  turbine  can  be  fully  appreciated,  the  unusual  capacity  for  so  small 
a  machine  being  due  to  the  great  speed  at  which  it  rotates.  (See 
Chapter  X  on  nozles  and  steam- velocity.) 

The  tremendous  velocity  which  steam  assumes  in  expanding  from 
ordinary  boiler-pressures  to  a  vacuum— 3,000  to  4,000  feet  per  second 
or  35  to  45  miles  per  minute — makes  the  use  of  a  single  wheel  impracti- 
cable for  turbines  of  large  power.  The  stresses  set  up  in  the  material 
of  the  wheel  by  centrifugal  force  prevent  the  employment  of  the 
peripheral  speeds  necessary  for  a  satisfactory  efficiency,  and,  except 
in  a  few  cases,  gearing  is  necessary  to  reduce  the  speed  to  a  point 
where  direct  connection  can  be  adopted. 

The  diagram  (Fig.  306)  shows  the  decrease  in  pounds  of  steam  used" 


.232 
^30 

I28 

S.22 

I20 
<J>  18 

•  — 

-  — 

Per  Cent  increase  of  Efficiency 

'  —  -, 

*•  -^ 

*** 

^ 

>^ 

i 

X 

1 

V 

/ 

\ 

.—  -  - 

.  - 

.  

.  - 

^^x**" 

24      6     8     10    12   14   16    18    20  22   24   26  28    30 

Inches  Vacuum 


FIG.  306. — Turbine-efficiency  with  increase  of  vacuum. 


324 


THE  STEAM-TURBINE 


per  kilowatt  hour  and  the  percentage  increase  in  efficiency  by  an 
increase  of  vacuum  in  a  steam-turbine.  It  shows  the  value  of  a  high 
vacuum. 

One  reason  why  the  vacuum  is  of  particular  value  to  a  turbine  is 
the  reduction  which  it  effects  in  the  windage.  A  top  will  spin  for  a 
remarkably  long  time  in  a  vacuum.  If  it  had  to  spin  in  an  atmos- 
phere of  compressed  air  or  high-pressure  steam,  its  motion  would 
last  for  a  comparatively  shorter  time.  -At  the  high  speed  at  which 
the  turbine  is  run  the  frictional  resistance  in  the  exhaust-pressure 
steam  must  be  considerable,  but  in  the  less  dense  atmosphere  of  the 
vacuum  much  less  of  the  energy  absorbed  is  used  in  overcoming 
friction,  and  adding  to  the  resulting  power  of  the  motor. 

In  Fig.  307  is  illustrated  a  recent  plan  of  a  De  Laval  steam- 
turbine  with  a  double  compensating  spiral  gear  and  connection  to 
a  multipolar  dynamo. 

We  illustrate  some  of  the  many  forms  or  models  in  which  experi- 
mental trials  have  been  made  that  have,  as  far  as  the  author  knows, 
not  brought  out  economical  results  in  their  practical  development. 
Fig.  308  shows  two  views,  and  a  section  of  the  blades,  of  a  Dow  steam- 
turbine,  in  which  two  disks  fixed  to  a  shaft  have  on  their  face  a  series 
of  circular  grooves  and  tongues,  meshed  with  a  pair  of  fixed  disks 

with  grooves  and  tongues,  as 
shown  in  the  small  section. 
The  tongues  on  the  revolving 
disks  are  cut  across  at  short 
distances  in  a  slanting  direc- 
tion. The  tongues  on  the  sta- 
tionary disk  are  cut  in  the 
opposite  direction.  The  steam 
passes  to  the  centre  hub,  and 
is  forced  through  the  openings 

across  the  tongues,  giving  motion  to  the  disks  and  shaft.  The  radial 
passage  of  the  steam  through  blades  of  varying  velocity  seems  a  bar 
to  efficiency. 

Another  curious  modification  in  construction,  the  Wilkinson 
steam-turbine  (Fig.  309),  consists  of  two  rim-pocketed  disks  running 
against  the  disk-surfaces  of  a  shell  with  oblique  steam-ports.  The 
disks  are  feathered  on  the  shaft,  and  held  against  the  faces  of  the  shell 


FIG.  308. — Dow  steam-turbine. 


THE  STEAM-TURBINE 


325 


and  the  steam-pressure  by  springs.  A  groove  around  the  shell  opposite 
the  pockets  allows  the  steam  to  pass  around  to  the  exhaust-pipes. 
The  shape  of  the  steam-pockets  and  -ports,  ra,  n,  in  the  rims  of  the 
disks  is  shown  in  the  section  at  the  right. 

An  experimental  turbine  by  Parsons  of  the  radial  impulse  type  is 
shown  in  Fig.  310,  in  which  a  series  of  disks  are  fixed  on  a  shaft  with 


FIG.  309. — Wilkinson  steam-turbine. 


FIG.  310. — Parsons  steam-turbine, 
early  type. 


intersecting  disks  on  the  shell.  The  face  of  the  shaft-disks  has  several 
small  blades  set  at  an  angle  with  the  radius.  The  outside  fixed 
disks  have  a  similar  set  of  blades  interlocking  with  the  revolving  blades 
and  set  at  a  contrary  angle.  The  steam  passes  from  the  valve  to  the 
inner  edge  of  the  first  fixed  disk,  then  outward  through  the  blades, 
and  returns  through  the  vacant  space  of  the  next  pair  and  outward 
again. 

This  form  of  the  Parsons  turbine  is  an  improvement  on  the  prin- 
ciple of  the  Dow  type  by  multiple  effect,  but  is  still  inefficient  as 
compared  with  the  later  types  of  axial  steam-flow. 


THE      MULTISTAGE      STEAM-TURBINE — 
PARSONS      TYPE 

In  Fig.  311  is  shown  a  sectional  view  of  one  of  the  earlier  models 
of  the  Parsons  turbine.  The  steam  is  admitted  to  the  chamber  A, 
encircling  the  cylinder,  from  the  governor-valve,  and  passes  along 
to  the  right  through  the  turbine-blades,  which  deflect  it  in  one  direc- 
tion, thence  striking  the  moving  blades  of  the  turbine,  which  deflect 
it  in  the  opposite  direction,  and  so  on.  In  this  way  the  current  of 


326  THE  STEAM-TURBINE 

steam  impinging  upon  the  moving  blades  drives  them  around.  The 
areas  of  the  passages  increase,  progressing  in  volume  corresponding 
with  the  expansion  of  the  steam.  On  the  left  of  the  steam-inlet 
are  revolving  balance-pistons,  C,  Ci,  C2,  one  corresponding  to  each 
of  the  cylinders  in  the  turbine.  The  entering  steam  at  A  presses 
equally  against  the  revolving  part  of  the  turbine  and  against  the 
first  balancing-piston.  When  it  arrives  at  the  passage  E  it  presses 
against  the  next  larger  section  of  the  revolving  part  of  the  turbine 
and  also  against  the  next  larger  balancing-piston,  connection  between 
the  two  being  secured  by  the  passage  F.  Similarly,  the  passage  G 
permits  the  balancing  of  the  largest  section  of  the  turbine.  By  a  proper 
arrangement  of  these  balancing-pistons  there  is  no  end-thrust  upon  the 


FIG.  311. — Parsons  steam-turbine. 

turbine-shaft  at  any  load  or  steam-pressure.  The  thrust-bearing  at 
H,  on  the  extreme  left,  is  to  take  care  of  accidental  thrusts  that  may 
arise  and  also  to  retain  the  alignment  of  the  shaft  accurately  so  as 
to  secure  the  correct  adjustment  of  the  balance-pistons. 

Since  these  balance-pistons  never  come  in  mechanical  contact 
with  the  cylinder  in  which  they  turn,  there  is  no  friction.  The  thrust- 
bearing  is  made  of  ample  size  and  is  subject  to  forced  lubrication. 

The  pipe  K  connects  the  chamber  back  of  the  balance-pistons 
with  the  exhaust-outlet,  so  as  to  insure  the  pressure  being  equal  at 
the  two  ends  of  the  turbine. 

The  bearings  J,  J  are  peculiar  in  construction.  Each  consists  of  a 
gun-metal  sleeve  prevented  from  turning  by  a  loose-fitting  dowel-pin. 
Outside  of  this  are  three  cylindrical  tubes  having  a  small  clearance 
between  them.  These  small  clearances  fill  up  with  oil  and  permit  a 


THE  STEAM-TURBINE 


327 


Stationary 


Stationary 


FIG.  312. — Stationary  and  running 
blades. 


slight  vibration  of  the  inner  shell,  while  at  the  same  time  restraining 

it  from  too  great  a  movement.     The  shaft  therefore  actually  revolves 

about  its  axis  of  gravity  instead  of  its  geometrical  axis,  as  would  be 

the   case  with   the  bearings  of  the 

usual  rigid  construction.    In  case  the 

shaft  is  a  little  out  of  balance  the 

journal  thus  permits  it  to  run  slightly 

eccentric.    The  forms  of  the  rotating 

and  stationary  blades  are  much  like 

those  of  the  Curtlss  type,  which  are 

detailed  in  Fig.  312. 

The  casing  of  the  turbine  is  lined 
with  disks  of  blades  curved  in  reverse 
of  the  blades  on  the  rotor;  all  of 
their  surfaces  are  of  approximately 
parabolic  form,  as  shown  in  the  cut. 

In    Fig.    313    is    represented    a 

vertical  section  of  the  later  Parsons  turbine  as  built  by  the  Westing- 
house  Machine  Company,  The  steam  from  the  governor-valve  V 
enters  the  neck  of  the  rotor  at  A  through  ports  around  the  shell,  and 
passes  to  the  left  through  the  successive  disks  of  stationary  and 
revolving  blades.  The  area  of  the  passage  between  the  blades  is 
continually  enlarged  to  meet  the  increasing  volume  of  steam  by  its 
expansion,  by  increasing  their  length,  and  in  stepping  up  in  area  by 
enlarging  the  diameter  of  the  rotor,  until  finally  it  is  exhausted  into 
the  chamber  B  and  into  the  condenser. 

By  this  traverse  of  the  steam  there  are  the  initial  pressure  upon 
one  end  of  the  series  of  rotating  blades  and  a  vacuum  on  the  other, 
the  difference  tending  to  press  the  rotor  toward  the  low-pressure  end. 
This  thrust  is  counterbalanced  by  a  series  of  balancing-disks,  P,  P,  P, 
equal  in  diameter  to  the  respective  sections  of  the  drum.  The  steam 
enters  between  the  smallest  of  these  disks  and  the  first  ring  of  blades, 
and  tends  to  push  the  disk  to  the  right  as  much  as  the  blade  to  the 
left,  and  from  the  chamber,  before  each  enlargement  of  the  drum, 
an  equalizing-pipe  or  -passage,  E,  leads  to  the  corresponding  balancing- 
disk.  A  similar  pipe  connects  the  vacuum-chamber  with  the  back 
of  the  largest  disk,  so  that  the  pressures  are  effectually  balanced. 
The  balancing-disks  are  finely  grooved  on  the  rims  and  run  in  the 


THE  STEAM-TURBINE  329 

grooved  pockets  of  the  casing.  A  small  thrust-bearing  takes  care 
of  any  incidental  tendency  to  move  endwise,  and  adjustment  is  pro- 
vided for  the  relative  positions  of  the  blades. 

The  principle  of  action  in  this  turbine  is  that  the  steam  of  the 
initial  pressure  is  admitted  upon  one  side  of  the  smallest  ring  and, 
flowing  through  the  spaces  formed  by  the  blades,  impinges  upon  the 
first  ring  of  rotating  blades,  giving  them  motion  by  its  impact.  But 
the  pressure  upon  the  exhaust  side  of  the  rotating  blade  is  less  than 
that  upon  its  intake  side,  and  the  steam  goes  on  expanding  in  the 
spaces  between  the  blades  and  issues  from  them  with  a  considerable 
velocity,  adding  its  reaction  effect  to  that  of  impact.  Reversed  in 
the  next  set  of  stationary  blades,  in  which  its  expansion  continues,  it 
impacts  upon  the  next  ring  of  moving  blades,  and  so  on  through 
the  turbine,  the  space  between  the  blades  increasing  progressively  by 
their  increasing  length. 

The  admission-port  for  steam  is  shown  at  S.  A  secondary  governor- 
valve  (shown  at  Vs)  from  the  admission-port  provides  for  admitting 
high-pressure  steam  directly  to  the  second  expansion  stage  when  the 
turbine  is  to  carry  heavy  overloads  or  if  the  vacuum  fails  from  any 
cause. 

Regulation  is  accomplished  by  means  of  a  constantly  moving 
pilot-valve  controlled  by  a  fly  ball-governor.  The  governor-levers 
are  mounted  on  knife-edges  instead  of  pins,  to  secure  sensitiveness. 
Speed  may  be  regulated  while  the  governor  is  in  motion.  This  is 
particularly  useful  for  synchronizing  the  speed  of  alternating-current 
machines  operated  in  parallel  and  for  adjusting  their  differences  of 
load  when  so  operated. 

The  pilot-valve  controls  the  admission-valves,  which  are  of  the 
balanced  vertical  lift  poppet  type. 

Steam  is  admitted  to  the  turbine  in  puffs  by  means  of  a  cam  on 
the  governor  and  a  spring-operated  piston,  a  steam-relay  making 
about  three  impulses  per  second. 

High-pressure  steam  is  admitted  at  all  loads,  and  the  admission- 
steam  is  not  throttled  in  proportion  to  the  load.  At  full  load  the  steam- 
puffs  merge  into  an  almost  continuous  flow. 

The  governor-  and  pilot-valve  are  operated  by  a  worm-gearing 
on  the  main  shaft.  The  pilot-valve  has  no  "  inertia  of  rest/'  and 
does  not  stick. 


330 


THE  STEAM-TURBINE 


On  the  larger  machines  a  speed-limit  governor  is  arranged  to  in- 
stantly shut  off  the  steam-supply  whenever  a  predetermined  limit 
of  speed  above  normal  is  reached. 

Frictionless  glands  at  the  ends  of  the  stator  prevent  the  admission 
of  air  or  the  escape  of  steam. 

The  rotating  disks  revolve  within  the  stator  with  a  close  fit  but 
not  in  contact.  The  adjacent  surfaces  are  provided  with  frictionless 
packing-rings.  These  offer  a  devious  path  for  the  steam,  and  leakage 
past  them  is  inappreciable. 

A  flexible  sleeve-coupling  connects  the  turbine  to  its  generator. 

Oil  for  the  turbine-  and  generator-bearings  is  raised  by  a  small 
plunger-pump  from  a  main  reservoir  in  the  bedplate  and  circulates 
by  gravity.  It  is  cooled  by  water-coils. 

The  Westinghouse-Parsons  turbine  utilizes  the  full  steam-energy 
and  does  this  at  rotative  speeds  well  within  commercial  requirements. 
These  speeds  do  not  exceed  3,600  turns  a  minute  for  the  400-kilowatt 
unit.  For  the  larger  units  the  number  of  turns  is  less.  The  steam 
is  also  robbed  of  all  power  of  erosion  by  having  its  velocity  gradually 
reduced  as  it  passes  through  the  turbine. 


TABLE  XXXIX. — GIVES  THE  EFFICIENCY-TESTS  OF  A  SOO-KILOWATT,  WESTING- 
HOUSE-PARSONS  TURBINE,  AND  SHOWS  THE  RELATIVE  STEAM-CONSUMPTION 
FOR  SATURATED  AND  SUPERHEATED  STEAM  AND  FOR  VARYING  VACUUM. 


TEST. 

LOAT>. 

STEAM. 

STEAM-CONSUMPTION. 

No. 

Proportion 
of 
capacity. 

B.  H.-P. 

Pressure, 
pounds. 

Quality. 

Vacuum, 
inches 
absolute. 

Total 
pounds 
per  hour. 

Pounds  per 
B.  H.-P. 
hour. 

1 
2 
3 

| 

Full 

396.0 
584.3 
762.3 

Sa 

151.2 
152.6 
153.2 

turated  stea 
99.47 
99.50 
99.45 

m. 
28.03 
28.03 
27.70 

5,908 
8,211 
10,429 

14.92 
14.05 
13.68 

5 

Full 

763.9 

Sup 

153.3 

(105. 

erheated  ste 

am 
28.00 
heat.) 

9,334 

12.22 

2°  F.  super 

6 
4 

7 

Full 

u 

Full 

722.9 
1,145.5 

678.7 

Re 

148.8 
142.6 
148.9 

duced  vacm 
99.53 
99.58 
99.73 

im. 
26.03 
26.30 
24.10 

10,781 
10,429 
10,764 

14.91 
15.08 
15.86 

THE  STEAM-TURBINE 


331 


An  efficiency-test  of  a  1,250-kilowatt  turbine  of  the  above  type 
consumed  27  pounds  of  steam,  without  vacuum  or  superheat,  per 
brake  horse-power  and  890  brake  horse-power  load,  and  24  pounds 
at  1,260  brake  horse-power  load,  150  pounds  initial  pressure. 

The  governor-valve  used  on  the  Parsons  turbine  varies  in  con- 
struction somewhat  with  the  different  builders  of  steam-turbines, 
and  may  be  called  properly  a  relay  or  vibrating  valve.  It  consists 
essentially  of  a  double-beat  or  balanced  valve  operated  by  a  small 
piston  and  spring,  with  its  opening  and  vibration  both  operated  from 
the  governor.  In  Fig. 
314  is  illustrated  the 
vibrating  valve-gear,  in 
which  the  double-beat 
valve  V  is  shown  closed. 
The  spindle  of  this  valve 
projects  upward  and  car- 
ries a  small  piston,  B, 
which  is  enclosed  in  a 
cylinder  and  held  in  its 
lowest  position  by  means 
of  a  spiral  spring,  F.  In 
the  bottom  of  the  cylin- 
der there  is  a  small  hole, 
O,  through  which  steam 
flows  under  the  piston  B 
when  the  main  valve  E 
is  opened,  so  that  the 

piston  is  lifted  up  and  at  the  same  time  the  double-beat  valve  V 
is  opened.  Steam  can  now  flow  into  the  turbine  at  A.  The  double- 
beat  valve  V  will  now  remain  open  as  long  as  there  is  steam  below 
the  piston  B.  In  order  to  allow  this  steam  to  escape  from  time 
to  time,  there  is  another  port-hole,  D,  which  is  considerably  larger 
than  the  steam-inlet  0.  The  port-hole  D  is  kept  closed  by  means 
of  a  small  piston,  G,  which  is  periodically  lifted  in  a  regular  jigging 
motion  by  the  eccentric  X,  which  is  directly  connected  to  the  gov- 
ernor-spindle, so  that  steam  escapes  from  the  cylinder  at  D  through 
the  pipe  H.  The  spring  S  now  overcomes  the  piston  B,  which  descends, 
thereby  closing  the  double-beat  valve  V.  Shortly  after,  the  piston  G  is 


FIG.  314. — Vibrating  valve-gear  of  the  Parsons 
steam-turbine. 


332  THE  STEAM-TURBINE 

again  pushed  downward  and  the  hole  D  closed,  whereupon  steam  again 
forces  up  the  piston  B,  so  that  the  double-beat  valve  is  once  more 
opened.  As  the  motion  of  the  piston  G  is  obtained  from  the  eccentric 
X,  the  number  of  lifts  bears  a  fixed  ratio  to  the  speed  of  the  turbine, 
and  the  number  of  gusts  of  steam  is  therefore  also  proportional  thereto. 
The  general  disposition  of  the  governor-gear  is  clearly  shown  in  the  cut. 


Half  Load  "5132 


Atmospheric  Line 


Full  Load 


MAW 


Atmospheric  Line 


Pressure  Removed  by  Condenser  £"-         I        Pressure  Removed  by  Condenser 

12. 77  Pounds  12.77  Pounds 

FIG.  315. — Variation  in  pressure  of  puffs  at  half  and  full  loads. 

Fig.  315  shows  indicator-diagrams  illustrating  the  variation  of 
pressure  due  to  the  vibration  of  the  relay  or  double  beat  valve  at  the 
steam-entrance  A  in  Fig.  314.  The  abscissa  or  frequency  are  a  func- 
tion of  time,  and  their  length  depends  upon  the  speed  for  which  the 
indicator-gear  was  set. 


THE      CURTISS      STEAM-TURBINE 

The  Curtiss  type  of  steam-turbine  is  assumed  to  be  a  combination 
of  the  principles  of  action  of  the  De  Laval  and  Parsons  types,  in  that 
the  first  impact  of  the  steam  is  from  a  series  of  several  expanding 
nozles,  in  groups  of  two  or  three,  at  equal  distances  around  the  revolv- 
ing wheel,  directly  upon  the  revolving  blades,  and  from  a  reaction  by  a 
fixed-blade  disk,  and  in  that  a  further  impact  occurs  upon  the  second 
revolving  wheel-blades,  the  steam  thus  expanding  through  two  or  three 
stages,  and  terminating  in  the  condenser.  The  vertical  arrangement 
of  the  shaft,  with  the  horizontal  plane  of  motion,  is  one  of  the  dis- 
tinctive features  of  the  Curtiss  turbine. 

In  Fig.  316  is  shown  an  elevation  of  a  two-stage  turbine  with  three 
sets  of  nozles  equally  divided  around  the  periphery  of  the  wheels. 
Each  of  the  five  or  more  nozles  in  each  set  is  of  the  expanding  form, 
with  rectangular  apertures  extending  across  the  wheel-blade  width. 
Steam  enters  through  the  series  of  nozles,  forming  a  broad  belt  of 


THE  STEAM-TURBINE 


333 


steam,  and  the  quantity  admitted  is  regulated  by  a  series  of  poppet- 
valves,  one  for  each  nozle.  Regulation  is  effected  by  opening  or  clos- 
ing these  valves  automatically,  and  for  fine  regulation,  involving  a 
less  quantity  of  steam  than  flows  through  any  one  nozle,  throttling 
in  one  nozle  is  resorted  to.  In  the  5,000-kilowatt  turbine  there  are 
three  sets  of  these  nozles,  spaced  at  60-degree  angles,  and  the  steam 
passes  through  three  sets  of  blades  into  an  intermediate  receiver, 
in  which  the  pressure  is  approximately  that  of  the  atmosphere. 
Thence  it  passes  through  a  second  set  of  guide-passages,  or  nozles, 
which  expand  the  steam  near- 
ly to  the  vacuum-pressure, 
and  the  velocity  of  the  steam 
is  abstracted  by  three  more 
sets  of  blades.  The  second 
row  of  nozles  occupies  the 
whole  circumference  of  the 
wheel,  to  allow  for  the  great 
volume  of  the  low-pressure 
steam. 

In  Fig.  317  are  shown  an 
outside  half-view  and  half- 
section  of  the  Curtiss  turbine, 
with  a  four-stage  expansion 
and  two  sets  of  multi-nozles. 
The  path  of  the  steam  through 
the  turbine  is  indicated  in  the 


FIG.  316. — Two-stage  Curtiss  turbine. 


drawing,  which  shows  also  the 
four  stages  into  which  the 
turbine  is  divided.  From  the  steam-chest  the  steam  passes  through 
poppet-valves  to  the  nozles  which  direct  it  upon  the  vanes  of  the  first 
of  the  moving  wheels  of  that  stage,  then  to  the  stationary  guide-vanes, 
then  to  the  second  moving  wheel,  from  which  it  passes  over  the  second 
set  of  guide-vanes  to  the  third  moving  wheel.  At  this  point  the  steam 
enters  the  third  set  of  guide-vanes  and  undergoes  a  similar  operation, 
finally  passing  out  at  the  bottom  of  the  turbine  into  a  condenser. 

In  the  first  stage  the  nozles  occupy  but  one-sixth  of  the  circum- 
ference, and  are  divided  into  two  equal  sets  in  the  turbine  illustrated. 
In  the  500-kilowatt  size  the  nozles  are  all  grouped  together;  in  inter- 


334 


THE  STEAM-TURBINE 


mediate  sizes  they  are  divided  into  two,  and  in  the  5,000-kilowatt  size 
into  three,  groups  equally  spaced.  The  first  intermediate  guides  in 
all  machines  are  grouped  in  the  same  manner  as  the  nozles  and  occupy 
the  same  circumferential  length.  In  the  second  and  third  stages 
the  nozles  and  intermediate  guides  generally  occupy  the  entire  circum- 
ference. 

The  nozles  are  cored  or  cut  passages  in  a  cast  plate,  forming,  in 
the  first  stage,  the  bottom  of  a  steam-chest  over  the  periphery  of  the 

turbine-wheel.  The  nozles  of  the 
second  stage  are  secured  to  a  dia- 
phragm separating  the  two  stages. 
The  nozle-openings  of  this  stage  are 
adjusted  to  maintain  the  pressure- 
relation  between  the  two  stages,  or 
to  shut  off  the  second  stage  entirely 
when  the  turbine  is  run  non-con- 
densing. This  adjustment,  which 
remains  permanent  for  an  approxi- 
mately fixed  condition  of  load,  is 
secured  by  means  of  a  register-ring 
rotating  through  a  small  angle.  The 
nozles  of  each  stage  are  so  propor- 
tioned that  the  steam,  when  it 
strikes  the  blades,  has  a  pressure 
but  slightly  above  the  exhaust,  and 
this  pressure  is  reduced  in  passage 
through  the  wheels  and  guides  to 
about  the  exhaust-pressure. 

In  Fig.  318  is  shown  the  arrange- 
ment of  the  steam-chest,  valves, 
nozles,  and  moving  and  stationary 
blades  for  a  three-stage  turbine.  The 
most  vital  points  in  a  steam-turbine 
are  the  buckets,  since  they,  and  the  spaces  between  them,  must  be 
shaped  exactly  right  to  give  the  correct  direction  of  flow  and  highest 
mechanical  efficiency,  and  also  to  provide  for  the  progressive  expansion 
of  the  steam.  The  buckets  of  the  Curtiss  turbine  are  cut  out  of  the 
solid  metal  by  special  bucket-cutting  machines.  For  the  smaller  sizes 


FIG.  317.— Half-section  of  Curtiss 
turbine. 


THE  STEAM-TURBINE 


335 


of  wheels  the  blades  are  cut  from  the  disks  comprising  the  wheels,  and 
for  the  larger  sizes  the  buckets  are  cut  from  segments  of  steel  and 
then  bolted  around  the  periphery  of  the  disks. 


STEAM  CHEST 


NOZZLE 


MOVING  BLADES 
STATIONARY  BLADES 
MOVING  BLADES 


MOVING  BLADES 


STATIONARY 
BLADES 


MOVING  BLADES 


STATIONARY 

BLADES 


MOVING  BLADES 


1     !     I 

FIG.  318. — Arrangement  of  nozles  and  blades. 

Fig.  319  shows  a  bucket-  or  blade-segment,  with  a  rim  of  steel 
riveted  on  and  enclosing  the  outer  openings  of  the  curved  passages 
in  the  buckets. 


FIG.  319. — Bucket-segment. 

In  Figs.  320  and  321  are  shown  the  elevation  and  plan  of  the  com- 
plete installation  of  the  2,000-kilowatt  Curtiss  turbine  at  the  St. 
Louis  Exposition.  The  plant  consists  of  a  two-stage  turbine,  with 


336 


THE   STEAM-TURBINE 


two  sets  of  ten  nozle-ports  on  opposite  sides  and  an  electric  control 
of  the  nozle-valves ;  a  small  turbine-driven  exciter-dynamo,  a  vacuum 


DRY  VACUUM  PUH 


FIG.  320. — 2,000-kilowatt  Curtiss  turbine  and  generator. 

pump,  a  not-water  pump,  an  oil-pump,  and  an  air-cooler.  The  normal 
speed  of  the  turbine  and  generator  was  about  800  revolutions  per 
minute,  with  an  initial  pressure  of  175  pounds. 

There  are  no  oil-cups,  and  no  hand-oiling  is  required,  all  lubrication 


FIG.  321.— Plan  of  turbine-plant. 


THE  STEAM-TURBINE 


337 


being  performed  by  a  circulating  system,  power  for  which  is  furnished 
by  a  steam-driven  oil-pump  capable  of  delivering  7J  gallons  of  oil 
per  minute  against  a  pressure  of  500  pounds  per  square  inch.  This 
pressure  is  maintained  below  the  step-bearing,  while  a  baffler  allows 
a  small  quantity  of  oil  at  a  low  pressure  to  rise  to  a  small  tank  on  the 
top  of  the  machine,  whence  it  flows  by  gravity  to  the  top  and  middle 
guide-bearings.  There  is  a  combined  reservoir  and  cooling-tank  in 
this  oiling  system  of  100  gallons  capacity.  Absolutely  no  cylinder-oil 
is  used  within  the  turbine,  nor  does  any  oil  mingle  with  the  steam. 

The  most  interesting  of  the  auxiliaries  is  the  25-kilowatt  direct- 
connected  horizontal  type  turbine-driven  exciter,  making  3,600 
revolutions  per  minute  and  furnishing  direct  current  at  125  volts. 
This  machine  is  of  the  single-stage  type,  having  three  rows  of  buckets 


FIG.  322. — Slide-valve  regulation. 

on  the  wheel  and  runs  non-condensing.  It  is  governed  with  a  throt- 
tle-governor, and  maintains  a  practically  constant  speed  and  voltage 
from  no  load  to  full  load.  It  has  a  forced  lubricating  system  of  its 
own,  operated  by  gear  from  the  generator  end  of  the  shaft. 

In  starting  up  either  the  large  or  small  turbine,  the  operator 
merely  opens  wide  the  main  steam-valve,  after  which  both  machines 
take  entire  care  of  themselves,  whether  running  light  or  carrying  a 
heavy,  fluctuating  load. 

In  Fig.  322  is  shown  in  section  the  slide-valve  system  of  regulating 
the  flow  of  steam  to  the  vanes  of  a  two-stage  Curtiss  turbine  of  recent 
model. 


338 


THE  STEAM-TURBINE 


In  Fig.  323  is  illustrated  a  novel  arrangement  by  which  the  buckets 
on  each  disk  are  doubled  in  effect,  producing  eight  stages  of  impact 
and  reaction  in  a  four-disk  turbine.  The  exhaust-steam  from  the 
first  disk  of  two  sets  of  running  buckets  and  intervening  stationary 
buckets  is  passed,  through  an  outside  chamber  with  automatic  valves, 
to  the  second  and  third  disks,  and  thence  direct  through  the  buckets 
of  the  fourth  disk.  The  area  of  the  buckets  throughout  the  system 
is  expanded  by  lengthening  to  meet  the  requirement  of  the  expanding 
volume  of  the  steam. 


FIG.  323. — Reenforcement  in  four-stage  turbine  by  double  buckets  on  each  disk. 

For  this  construction  the  rim  of  each  disk  is  made  wide  enough 
to  receive  the  stationary-bucket  sections  and  their  clearance.  The 
disk-buckets  are  flanged  and  bolted  to  each  side  of  the  disks.  The 
stationary  buckets  are  fixed  in  grooves  in  the  shell. 

The  vertical  position  of  the  shaft  in  the  Curtiss  turbine  throws 
great  weight  upon  the  shaft-step,  which  with  any  ordinary  form  of 
step-bearing  would  become  an  insurmountable  obstacle  to  this  posi- 
tion of  the  turbine. 

In  Fig.  324  is  shown  a  section  of  the  step  and  adjustments  as  de- 
signed for  the  Curtiss  turbine.  The  bearing  consists  of  two  hard 
cast-iron  blocks,  one  carried  by  the  end  of  the  shaft  and  fixed  by 
dowels  and  key.  The  lower  block  is  fitted  to  the  follower,  and  is 


THE  STEAM-TURBINE 


339 


supported  by  a  powerful  screw  driven  by  a  wheel,  and  is  provided 
with  worm-gear  for  adjustment. 

This  block  is  recessed  to  about  half  its  diameter,  and  into  this  recess 
oil  is  forced  with  sufficient  pressure  to  balance  the  weight  of  the  whole 
revolving  element.  The  amount 
of  oil  required  is  small.  About  4 
gallons  per  minute  is  used  in  the 
5,000-kilowatt  machine.  A  water 
circulation  in  the  main  step-block 
keeps  all  the  bearings  cool. 

The  oil,  after  passing  between 
the  blocks  of  step-bearing,  wells 
upward  and  lubricates  a  step-bear- 
ing supported  by  the  same  casting. 
This  whole  structure  is  inside  the 
base,  and  a  packing  is  used  between 
the  oil-chamber  and  the  base,  so 
that  oil  or  air  cannot  get  into  the 
vacuum-chamber.  A  small  steam- 
pressure  is  maintained  between  the 
sections  of  this  packing,  in  order 

that  these  objects  may  be  accom-  FlG  324.— Turbine-step, 

plished  with  certainty.     In  many 

cases  these  same  step-bearings  have  been  operated  with  water  instead 
of  oil,  in  which  case  no  packing  is  necessary,  the  water  being  allowed 
to  pass  into  the  base. 


THE     RATEAU     STEAM-TURBINE 

The  steam-turbine  designed  by  A.  Rateau  and  made  principally 
in  France  and  Germany,  is  a  horizontal  turbine  of  the  axial-impulse 
type,  with  the  blades  of  the  same  form  as  those  of  the  De  Laval, 
Curtiss,  and  Parsons  models,  but  differing  in  constructive  detail. 
The  bucket-orifices  are  enlarged  progressively,  as  in  the  Parsons  and 
Curtiss  turbines,  by  lengthening  the  blades  of  both  elements. 

The  revolving  wheels  are  formed  of  disks  of  thin  sheet  steel,  carry- 
ing cylindrical  buckets  on  the  periphery,  these  buckets  being  riveted 
to  a  band  of  steel  welded  to  the  disk.  This  gives  a  very  light 


340 


THE  STEAM-TURBINE 


and  strong  construction,  maintaining  its  balance  at  all  speeds.  The 
guide-buckets  are  fixed  in  circular  diaphragms,  secured  at  the  pe- 
riphery in  grooves  cut  in  the  interior  of  the  turbine-case.  There  is 
thus  left  between  the  successive  diaphragms  a  series  of  annular  cham- 
bers in  which  the  revolving  wheels  are  placed.  The  shaft  passes 
through  bushings  fitted  in  the  diaphragms,  there  being  but  little 


Ste 


FIG.  325. — Rateau  steam-turbine. 

play  or  clearance.  Between  the  fixed  and  revolving  portions  of  the 
turbine,  however,  the  clearance  may  readily  be  made  as  much  as  5 
millimetres,  without  injury.  The  main  bearings  of  the  shaft  are 
outside  the  casing,  a  special  form  of  stuffing-box  being  employed, 
assuring  tightness  against  leakage. 

An  ordinary  compensated  centrifugal  governor  is  used  to  regulate 
the  speed,  acting  by  varying  the  pressure  of  the  steam  delivered  to  the 
turbine.  By  means  of  a  by-pass  in  the  main  steam-pipe  it  is  possible 
to  deliver  steam  of  full  pressure  both  to  the  entrance  of  the  turbine 
at  A,  and  to  a  point  in  the  machine  nearer  to  the  condenser,  this  en- 
abling a  higher  power  than  the  normal  amount  to  be  produced  by 
the  machine,  much  in  the  same  manner  as  a  compound  engine  may 
be  used  with  full-pressure  steam  in  both  high-  and  low-pressure 
cylinders. 


THE  STEAM-TURBINE 


341 


THE     ZOELLY     STEAM-TURBINE 

Among  the  many  different  types  or  models  of  turbines  built  in 
Europe,  we  illustrate  in  Fig.  326  a  Swiss  duplex  turbine,  constructed 
by  Escher,  Wyss  &  Co.,  of  Zurich,  the  builders  of  the  first  Niagara 
water-turbines,  a  type  since  adopted  by  American. builders.  It  is  of 
the  Zoelly  design,  and  divided  into  two  compartments,  alike  in  detail, 
but  one  is  adapted  to  a  high-  and  the  other  to  a  low-pressure  steam- 
range. 

The  Zurich  turbine  is  of  the  multistage  impulse  type,  the  expan- 
sion of  steam  taking  place  in  the  passages  between  the  wheels,  and  the 
force  on  the  moving  wheels  being  exerted  by  impact  of  the  rapidly 
flowing  steam-jet.  On  the  high-pressure  wheels,  steam  is  admitted 
to  buckets  around  only  part  of  the  circumference,  while  on  the  low- 
pressure  wheels  the  admission  is  to  all  buckets.  The  high-  and  low- 
pressure  ends  are  mounted  independently  on  a  single  base,  connection 


FIG.  326. — View  and  section  of  Zoelly  steam-turbine. 

between  them  being  made  by  a  pipe  carried  beneath  the  turbine. 
The  main  bearings  are  outside  the  wheel-cases,  and  are  mounted  on 
the  base-plate  independently.  They  are  thus  kept  away  from  the 
heat  of  the  steam,  and  are  easily  accessible  for  inspection  and  repairs. 
The  wheels  are  built  up  of  open-hearth  steel  disks,  keyed  to  the 
shaft  and  having  on  the  outer  rim  a  ring  fastened  in  such  a  manner 


342 


THE  STEAM-TURBINE 


that  with  the  rim  of  the  disk  it  forms  a  dovetailed  groove.  The 
buckets  and  spacers  between  them  are  held  by  tongues  in  this  groove, 
and  project  radially  from  the  rim  of  the  disk.  The  buckets  are  of 
nickel  steel  highly  polished  to  reduce  friction,  as  are  also  the  disks. 

A  point  which  is  made  by  the  designer  is  that  the  blades  decrease 
in  cross-section  from  their  inner  to  their  outer  ends,  so  that  the  cen- 
trifugal force  is  kept  very  low,  and  the  blades  can  safely  be  made 
much  longer  than  if  they  were  of  uniform  cross-section.  Also  the 
blades,  which  act  as  a  cantilever-beam,  are  made  strongest  at  the 
point  where  the  bending  moment  due  to  steam-impact  is  greatest. 
The  curve  of  the  blades  is  such  as  is  needed  for  the  progressive  ex- 
pansion of  the  steam. 

This  special  construction  allows  of  running  the  wheels  at  a  high 
rim-speed,  thus  reducing  the  number  of  stages  needed  in  the  turbine, 
which  in  turn  allows  of  a  shorter  machine  and  of  lower  cost.  The 

guide-wheels  are  placed 
between  the  revolving 
wheels  and  are  carried 
from  the  outer  casing. 
On  account  of  the  shape 
of  the  guide-blades, 
shown  in  Fig.  327,  there 
is  a  considerable  endwise 
pressure  which  is  taken 
care  of  by  using  thick 
distance-pieces  project- 
ing outside  the  radial 
blades  of  the  moving  wheels  and  transmitting  the  end-thrust  from 
the  guide-disks  to  the  outer  end  of  the  casing.  The  general  arrange- 
ment of  wheels  and  guide-disks  is  shown  in  the  section  of  the  low- 
pressure  end,  and  the  detail  of  construction  in  the  larger. view. 
The  pressure  on  the  two  sides  of  the  revolving  disks  is  in  all  cases 
equal,  so  that  no  end-thrust  is  produced.  The  governor  is  of  the 
flyball  type,  and  operates  a  pilot-valve  controlling  the  motion  of  a 
plunger,  which  in  turn  operates  the  main  steam-valve,  thus  throttling 
the  pressure  of  the  steam.  The  water-pressure  for  operating  this 
plunger-valve  is  furnished  by  an  auxiliary  motor. 

We  cannot  give  space  to  all  the  types  or  models  of  steam-turbines 





FIG.  327. — Detail  of  wheel  and  guide-disk. 


THE   STEAM-TURBINE  343 

in  successful  operation;  some  of  them  will  no  doubt  become  permanent 
in  their  special  line  of  usefulness.  They  have  come  to  stay,  in  har- 
mony with  the  reciprocating  engine,  which  by  its  long  and  varied  trial 
has  standardized  it  for  every  use. 

THE      ROTARY     ENGINE 

In  regard  to  the  rotary  type  of  steam-engine  we  find  nothing 
worthy  of  illustration  or  description,  and  from  many  years'  experi- 
ence with  their  performance  and  lasting  qualities,  have  found  nothing 
as  yet  to  recommend  them,  being  inefficient  and  of  short  life;  yet  a 
few  small  ones  are  in  use.  We  have  left  them  to  the  tender  mercies 
of  their  inventors  and  promoters. 

The  Dake  engine,  now  in  use  for  small  units  of  power,  although 
called  a  rotary,  is  not  of  that  type,  but  a  combination  of  two  rectangu- 
lar pistons,  concentric  and  moving  at  right  angles  to  each  other,  of 
which  one  is  pivoted  to  a  crank  and  shaft  centring  within  a  rectangular 
case. 

The  contest  for  the  survival  of  the  fittest  types  of  prime  movers 
of  motive  power  in  the  future  will  finally  culminate  in  the  success 
due  to  efficiency  and  durability  in  the  various  fields  of  their  usefulness, 
and  no  one  type  can  become  universal. 

Nature's  elements,  wind  and  water,  with  steam  and  confined 
combustion  for  power,  are  the  only  and  real  bases  of  our  future  pros- 
perity in  the  production  of  primary  power,  in  which  each  is  prominent 
in  its  own  sphere  of  usefulness. 

THE     STARTING     AND     OPERATION     OF     LARGE 
STEAM-PLANTS 

Much  discussion  has  been  published  in  technical  journals  in  regard 
to  the  time  required  for  starting  large  steam-plants  of  the  recipro- 
cating and  turbine  types.  We  here  give  an  excerpt  from  a  published 
article  by  an  engineer  familiar  with  large  steam-plants: 

"So  much  has  been  written  about  the  sensitiveness  of  a  rotating 
disk  to  the  changes  of  temperature  and  the  effects  of  unequal  expan- 
sion that  it  is  easy  to  imagine  difficulties  in  the  rapid  start.  The 
possibilities  of  an  engine  with  a  62-inch  low-pressure  cylinder  in 


344  THE  STEAM-TURBINE 

starting  practically  cold  and  coming  up  to  synchronous  speed  are 
well  understood.  A  station-manager  would  criticise  an  engineer 
who  would  open  his  throttle  as  fast  as  he  dared  without  wrecking 
his  piping  system  and  let  his  machine  jump  into  her  work.  One  turn 
at  a  time  on  the  throttle  is  about  all  that  is  considered  safe,  and  even 
then  a  close  watch  is  kept  for  groaning  valves  and  cold  back  bonnets. 

"Every  time  the  starting-valve  is  moved  to  increase  the  steam- 
flow  the  engine  is  allowed  to  take  its  full  increment  of  speed,  due  to 
that  particular  throttle-position,  before  the  supply-valve  is  moved 
a  second  time.  There  are  ten  large  oil-cups,  and  frequently  more, 
that  must  be  opened  and  adjusted  before  the  machine  moves  at  all, 
besides  whatever  oiling  is  to  be  done  about  the  air-pumps  and  other 
auxiliary  apparatus. 

"Most  engineers  would  consider  ten  minutes  as  rather  a  fast  start 
and  fifteen  minutes  as  a  more  usual  starting-period,  including  time 
taken  for  warming  up;  in  fact,  it  may  not  be  overstating  the  case  to 
say  that  if  it  were  known  that  an  engine-driven  plant  were  to  be  called 
upon  in  emergency  for  power  and  it  were  essential  that  the  briefest 
possible  time  were  to  elapse  between  the  call  and  the  taking  of  the 
load,  one  or  more  engines  would  be  kept  in  motion  all  the  time, 
turning  slowly  and  hot  all  over. 

"This  question  makes  itself  very  prominent  when  the  steam- 
station  is  operated  as  an  auxiliary  to  a  large  source  of  high-tension 
power,  which  is  itself  in  the  construction  stage  and  has  a  large  over- 
load capacity  of  its  own  to  carry,  supplying  all  sorts  of  apparatus 
that  use  electric  power,  railway,  lighting,  and  power  circuits  simulta- 
neously. 

"At  such  a  time  all  sorts  of  accidents  will  happen  to  the  high- 
tension  water-driven  plant,  most  of  them  due  to  the  necessarily 
temporary  character  of  many  of  the  electrical  connections.  It  takes 
months  before  an  intricate  system  of  wiring  can  be  thoroughly  relied 
upon,  for  it  takes  months  before  the  temporary  work  of  construction 
can  be  replaced. 

"The  station  under  consideration  is  equipped  with  three  Curtiss 
turbine-driven  alternators,  40-cycle,  10,000  volts,  each  of  1,500  kilo- 
watts normal  capacity.  During  the  summer  months  the  station  is 
operated  as  an  auxiliary  to  a  water-power  plant,  taking  all  sudden 
overloads. 


THE  STEAM-TURBINE  345 

"A  signal  has  been  arranged,  a  j-inch  whistle,  so  that  it  can  be 
blown  instantly  should  the  power  fail.  A  blast  of  that  whistle 
means — cut  in  two  turbines  and  bring  the  third  up  to  speed.  The 
load  will  be  heavy,  and  all  auxiliary  apparatus  must  be  in  regular 
operation. 

"Each  turbine  has  a  surface-condenser,  and  there  are  three  or 
four  pumps  to  be  started  for  each  pair  of  turbines — one  circulating- 
pump,  one  combined  hot-well  and  feed-pump,  one  pressure-pump 
for  the  step-bearings,  and  one  dry  air-pump,  all  of  which  are  motor- 
driven.  The  exciter  is  driven  by  a  steam-engine  and  must  be  started 
also,  for  it  supplies  current  to  a  portion  of  the  auxiliary  apparatus. 

"The  boiler-room  has  steam  up  at  all  times,  supplying  a  system 
for  manufacturing  purposes  other  than  power,  and  slow  fires  are  kept 
in  enough  boilers  to  make  steam  needed  for  the  normal  load.  Forced 
load  means  forced  fires.  The  boilers  have  under  feed-stokers,  equipped 
with  pressure-blast,  and  will  respond  quickly  to  a  50-per-cent. -excess 
call  for  steam.  The  operating  force  for  this  is  about  equivalent  to 
a  force  for  an  engine-driven  plant.  Engineers  and  oilers,  however, 
are  busy  about  the  building  on  construction  work,  installing  new 
apparatus  and  taking  such  work  as  their  regular  occupation  when 
the  turbines  are  not  running. 

"At  the  sound  of  the  whistle  the  water- tender  starts  a  blower 
on  the  extra  row  of  boilers:  all  blast-dampers  are  opened  up  and  all 
stokers  are  allowed  to  feed  at  the  maximum  rate.  Each  fireman 
dumps  his  free  ash  and  bars  over  his  red  fire. 

"The  man  in  charge  of  the  coal-and-ash  conveyer  starts  the 
pressure-pump  for  step-bearings.  One  of  the  turbine  men  starts  the 
exciter  which  supplies  current  to  the  auxiliaries  beside  its  field-current; 
a  second  turbine  man  starts  the  circulating-pump  and  then  his  turbine. 
The  hot-well  pump  and  the  air-pump  are  started  by  the  oiler.  These 
movements  take  place  simultaneously.  The  force  is  organized  upon 
the  lines  that  obtain  in  a  fire-station ;  each  man  has  his  specific  duty, 
and  after  performing  it  looks  to  see  that  there  is  nothing  more  for 
him  to  do.  Only  a  few  seconds  elapse  between  starting  the  first 
pump  and  starting  the  first  turbine. 

"The  turbine-throttle  is  opened  as  fast  as  an  8-inch  steam-valve 
can  be  opened  without  endangering  the  steam-piping  system.  It  is 
not  considered  advisable  to  open  the  throttle-valve  as  fast  as  a  man's 


346  THE  STEAM-TURBINE 

strength  will  permit;  but  if  nothing  unusual  occurs  in  the  pipe-line, 
sentiment  does  not  spare  the  turbine. 

"One  electrician  attends  to  the  switchboard  and  telephone.  As 
soon  as  the  machine  approaches  speed,  the  synchronizing  system  is 
cut  in  and  the  main  switches  are  got  ready.  One  and  one-half  min- 
utes will  do  all  the  work  here  outlined,  including  the  time  taken  in 
mustering  the  crew  from  various  parts  of  the  building,  itself  not  a 
trivial  matter. 

"Manipulating  an  engine-regulator  so  that  it  shall  be  at  a  precise 
speed  and  at  an  exact  phase  relationship  from  some  other  machine, 
not  more  than  y^Vo"  Papt  of  a  second  removed  from  it,  is  no  matter  that 
can  be  hurried,  and  one  minute  is  fast  time  on  such  work.  But  the 
whole  thing,  phasing-in  and  all,  has  been  done  in  two  and  one-half 
minutes,  including  full  load  on  the  turbine,  which  started  from  a 
standstill. 

"This  performance  has  been  gone  through  a  great  many  times, 
and  our  record-book  shows  that  out  of  43  such  calls,  10  starts  were 
made  in  2J  minutes,  18  in  3  minutes,  and  15  in  3J  minutes. 

"We  have  taken  the  time  in  a  number  of  instances  when  all  the 
auxiliaries  have  been  in  motion  and  it  only  remained  to  start  the 
turbine  and  phase  it  in  on  the  line;  the  only  valves  to  open  in  such 
cases  are  the  throttle  and  one  small  oil-valve.  The  two  quickest 
starts  have  been  made  in  forty-five  seconds  and  seventy  seconds, 
respectively,  including  phasing-in.  Others  range  between  one  minute 
ten  seconds  and  one  and  one-half  minutes.  The  two  quickest  starts 
were  made  on  a  turbine  which  had  stood  for  twenty-four  hours  with 
the  throttle-valve  shut  tight,  though  there  was  a  slight  leakage  past 
the  seat.  After  the  throttle-valve  is  off  its  seat  it  is  not  more  than 
thirty  seconds  before  the  turbine  is  up  to  speed.  A  cross-compound 
reciprocating  engine  of  the  four-valve  type,  2,250  horse-power  ca- 
pacity, can  be  brought  up  to  speed  from  a  standstill  in  five  minutes  if 
it  is  hot  all  over.  This  five  minutes  is  to  be  compared  with  the  seventy 
seconds  required  for  the  similar  turbine  operation. 

"A  reciprocating  engine,  which  is  turning  over  slowly  with  the 
throttle-valve  just  off  its  seat  or  with  by-pass  open,  and  having  all 
its  oil-cups  open  and  regulated,  can  be  brought  up  to  speed — say, 
seventy-five  turns — in  two  and  one-half  minutes.  This  can  be  com- 
pared with  the  thirty  seconds  necessary  for  bringing  the  turbine  up 


THE  STEAM-TURBINE  347 

under  the  same  conditions;  that  is,  about  one-fifth  the  time  necessary 
for  bringing  up  the  engine. 

"If  the  engine  is  cold  all  over  and  has  all  its  oil-cups  shut  tight 
and  all  its  auxiliaries  quiet,  fifteen  minutes  is  called  a  rapid  start. 
Starts  have  been  made  under  such  conditions  in  twelve  minutes. 
When  we  start  a  cold  turbine,  we  open  up  the  valve  and  let  her  turn, 
and  in  two  minutes  we  are  ready  to  bring  her  up  to  speed,  and  she 
will  be  at  speed  in  two  and  one-half  minutes,  dividing  the  engine's 
time  by  more  than  four." 

The  points  of  practice  here  suggested  from  an  engineer's  experience 
in  operating  large  steam-plants  are  well  worthy  of  study  and  remem- 
brance by  all  engineers,  and  their  appeal  is  directly  urged  upon  the 
student,  who  may  profit  by  them  in  his  initial  trials.  Their  neglect 
has  caused  many  wrecks  in  expensive  installations  of  steam-power,  re- 
sulting not  only  in  the  expense  of  repairs,  but  often  the  delay  is  the 
most  expensive  item  in  the  wreckage  cost. 


CHAPTER    XX 

MECHANICAL    REFRIGERATION-ENGINEERING 

THE  principal  difficulties  encountered  in  becoming  a  competent 
engineer  in  charge  of  refrigerating-machinery  do  not  include  a  thor- 
ough comprehension  of  the  fundamental  principles,  but  are  found  in 
the  arrangement  of  the  piping  and  valves  of  which  the  greater  part 
of  the  system  consists.  It  requires  considerable  practice  to  learn 
what  to  do  and  when  to  do  it,  and  to  be  able  to  note  the  little  changes 
and  minor  adjustments  which  affect  the  economical  production  of  low 
temperatures. 

Refrigeration  in  principle  can  be  learned  without  special  effort, 
but  the  proper  manipulation  of  the  various  valves  and  knowing 
what  results  should  be  obtained  at  the  various  points  in  the  system 
require  the  assistance  of  an  experienced  person.  Even  practice  may 
be  obtained  without  special  instruction;  but  experimenting  with 
ammonia  is  usually  found  to  be  very  different  from  experimenting 
with  steam  or  water  under  like  pressures,  and  it  is  liable  to  lead  to 
accidents  and  unnecessary  expense. 

The  more  noticeable  effect  upon  the  general  demeanor  of  the  suc- 
cessful refrigerating-engineer,  due  to  a  thorough  knowledge  of  the 
peculiarities  and  requirements  of  ammonia,  is  that  of  making  him 
careful  and  thorough  in  every  detail  of  his  work.  Makeshifts  in  a 
refrigerating-plant  cannot  be  tolerated.  Whatever  is  done  must  be 
done  thoroughly,  in  order  to  avoid  increasing  annoyance,  if  not  un- 
necessary expense  and  actual  danger.  An  engineer  accustomed  to 
operating  a  refrigerating-plant  will  usually  be  found  a  careful  person 
in  any  plant.  Beside  this  he  will  have  broadened  his  knowledge  of 
the  compression  and  expansion  of  gases  and  of  the  generation  and 
removal  of  heat  and  its  effect  upon  various  substances  and  liquids; 
in  fact,  he  will  have  taken  another  step  forward  toward  the  mastery 
of  the  various  sciences  underlying  and  connected  with  steam-engin- 
eering. 
348 


MECHANICAL   REFRIGERATION-ENGINEERING  349 

Engineers  can  scarcely  expect  to  escape  refrigerating-machinery, 
no  matter  where  they  go.  Small  dairies  and  cheese-factories  located 
in  farming  districts,  abattoirs  on  country  roads;  in  fact,  any  estab- 
lishment large  enough  to  warrant  the  use  of  a  steam-boiler  and  in 
which  low  temperature  is  required  for  the  preservation  of  the  product 
is  likely  to,  and  oftentimes  does,  contain  a  refrigera ting-apparatus 
of  one  kind  or  another. 

Thus  mechanical  refrigeration  has  become  one  of  the  branches 
of  steam-engineering — one  that  has  made  a  considerable  demand 
upon  the  ingenuity  and  resourcefulness  of  the  engineer,  and  has 
become  so  important  a  part  of  the  engineer's  education  that  the  time 
is  not  far  distant  when  the  steam-engineer  will  not  be  considered 
thoroughly  competent  without  a  working  knowledge  of  both  the 
compression  and  the  absorption  system. 

ANHYDROUS     AMMONIA 

Ammonia  is  a  gas  composed  of  82.35  per  cent,  of  nitrogen  and 
17.65  per  cent,  of  hydrogen.  It  is  very  much  lighter  than  air,  its 
specific  gravity  being  0.589.  It  is  characterized  by  a  pungent,  suffo- 
cating odor,  and  by  its  high  solubility  in  water,  one  volume  of  water 
at  32°  F.  absorbing  1,050  volumes  of  gas.  This  solution  of  the  gas  in 
water  is  what  is  commonly  known  as  aqua  ammonia,  and  it  rather 
confuses  the  situation,  because  the  water-solution  of  gas  is  used  in 
the  absorption  system  of  refrigeration,  while  the  ammonia  used  in 
the  direct  expansion  and  compression  system  is  an  entirely  different 
product.  The  product  known  as  anhydrous  ammonia  is  the  gas 
itself  liquefied  by  intense  pressure.  It  has  absolutely  no  water  con- 
tent, and  is  strictly  analogous  to  liquid  air,  but  liquid  air  consists  of 
two  distinct  substances,  each  one  a  gas  liquefied  by  intense  pressure — 
that  is  to  say,  the  nitrogen  and  hydrogen  in  anhydrous  ammonia 
are  chemically  combined  to  a  single  substance,  while  in  liquid 
air  the  oxygen  and  nitrogen  composing  the  air  are  not  chemically 
combined. 

Anhydrous  ammonia  boils  at  a  fixed  temperature  of  28.6°  F. 
below  zero.  One  pound  of  liquid  ammonia  at  32°  F.  would  occupy 
21  cubic  feet  when  evaporated  to  a  gas  at  atmospheric  pressure,  and 
the  vaporization  of  a  pound  requires  555.5  British  thermal  units.  It 


350  MECHANICAL  REFRIGERATION-ENGINEERING 

is  a  colorless  and  very  mobile  liquid.  It  has  a  specific  gravity  of 
0.613  compared  with  water  at  60°  F.  A  cubic  foot  of  anhydrous 
ammonia  weighs  42.1  pounds. 

The  usual  method  of  detecting  impurities  is  by  evaporation  of  a 
measured  amount  of  the  substance.  The  residue  remains  in  the 
bottom  of  the  tube,  and  can  be  either  weighed  or  measured.  Not 
many  years  ago  it  was  quite  common  to  have  ammonia  containing 
as  high  as  15  per  cent,  of  impurities;  to-day  commercial  ammonia 
rarely  contains  0.5  per  cent,  of  impurities.  It  is  stated  that  Armour's 
anhydrous  ammonia  does  not  exceed  0.1  per  cent,  of  impurities,  and 
usually  but  the  merest  trace.  Impurities  amounting  to  2  per  cent, 
are  detrimental,  as  they  affect  the  refrigerating  value  of  anhydrous 
ammonia.  Impurities  of  0.1  per  cent,  or  less  can  be  disregarded.  It 
is  true  these  impurities  accumulate  in  the  system,  but  when  the 
amount  is  but  0.1  per  cent.,  this  has  little  effect  on  the  action  of 
ammonia  in  the  refrigerating-plant,  and  its  accumulation  is  very 
slow. 

Without  going  into  a  discussion  of  the  availability  of  the  several 
different  gases  for  refrigerating  purposes,  it  may  be  said  that  ammonia 
combines  the  required  characteristics  and  therefore  is  found  to  be 
most  suitable;  for  when  we  consider  the  pressures  at  which  other 
gases  can  be  made  to  liquefy  when  at  ordinary  temperatures  and  the 
amount  of  cold  water  that  otherwise  would  be  required,  together 
with  the  important  item  of  safety  or  the  absence  of  dangerous  qual- 
ities, it  is  easily  understood  why  ammonia  is  best  adapted  to  the  pur- 
pose. Therefore  we  will  consider  the  ammonia  compression  system 
of  refrigeration  from  the  standpoint  of  the  engineer  in  charge  of  the 
machinery  and  whose  success  in  handling  it  will  be  directly  in  pro- 
portion to  his  knowledge  of  the  principles  involved,  together  with 
the  details  of  the  machinery  and  the  care  bestowed  upon  it. 

When  ammonia  is  received  ready  for  the  system  it  is  in  the  liquid 
state  enclosed  in  steel  drums,  which  are  only  partly  filled,  leaving 
space  enough  for  expansion  so  as  to  prevent  an  explosion  of  the  drums. 
Ammonia-drums  have  exploded,  but  always  under  conditions  of 
overheating,  for  in  general,  with  proper  care,  there  is  no  danger. 
When  liquid  ammonia  evaporates  into  gas  under  a  lower  pressure, 
heat  must  be  added  to  supply  the  latent  heat  of  the  gas  corresponding 
to  that  pressure  and  temperature.  The  latent  heat  of  the  gas  and 


MECHANICAL   REFRIGERATION-ENGINEERING 


351 


many  other  points  regarding  pressures  and  temperatures  may  be  found 
from  the  following  table,  which  gives  the  more  important  properties 
of  ammonia. 


TABLE  XL. — PROPERTIES  OF  AMMONIA. 


Gauge-pres- 
sure, pounds 
per  square 
inch. 

Absolute  pres- 
sure, pounds 
per  square 
inch. 

Temperature, 
degrees  F. 

Absolute  tem- 
perature, 
degrees  F. 

Latent  heat  of 
evaporation  in 
thermal  units. 

Volume  of  1 
pound  vapor 
in  cubic  feet. 

-t! 

«-+j  cj  • 

°§^! 

r**+-t  O  fl 

fe&g 

^ra 

Volume  of  1 
pound  of  liquid 
in  cubic  feet. 

Weight  of  1 
cubic  foot  of 
liquid  in 
pounds. 

-4.01 
-2.39 
-0.57 
1.47 
3.75 

10.69 
12.31 
14.13 
16.17 
18.45 

-40 

-35 
-30 
-25 
-20 

420.66 
425.66 
430.66 
435.66 
440.66 

579.97 
576.68 
573.69 
570.68 
567.67 

24.38 

21.32 
18.69 
16.44 
14.51 

.0410 
.0469 
.0535 
.0608 
.0690 

.0234 
.0236 
.0237 
.0238 
.0240 

42.589 
42.337 
42  .  123 
41.858 
41.615 

6.29 
9.16 
12.22 
15.67 
19.46 

20.99 
23.80 
26.92 
30.37 
34.16 

-15 
-16 
-  5 
0 
5 

445.66 
450.66 
455.66 
460.66 
465.66 

549.35 
546.26 
543  .  15 
540.03 
536.91 

7.23 
9.49 

5.84 
5.27 
4.76 

.1383 
.1541 
.1711 
.1897 
.2099 

.0243 
.0250 
.0252 
.0253 
.0255 

41.375 
41.135 
40.895 
40.655 
40.415 

23.64 
28.24 
33.25 
38.73 
44.72 

38.34 
42.94 
47.95 
53.43 
59.42 

10 
15 
20 
25 
30 

470.66 
475.66 
480.66 
485.66 
490.66 

549.35 
546.26 
543.15 
540.03 
536.91 

7.23 

6.49 
5.84 
5.27 
4.76 

.1373 
.1541 
.1711 
.1897 
.2099 

.0249 
.0250 
.0252 
.0253 
.0255 

40.160 
39.920 
39.682 
39.432 
39.200 

51.22 
58.29 
65.96 
74.26 
83.22 

65.92 
72.99 
80.66 
88.96 
97.92 

35 
40 
45 
50 
55 

495.66 
500.66 
505.66 
510.66 
515.66 

533.78 
530.63 
527.47 
524.30 
521.12 

4.31 
3.91 
3.56 
3.24 
2.96 

.2318 
.2554 
.2809 
.3084 
.3380 

.0256 
.0258 
.0260 
.0261 
.0263 

38.950 
38.700 
38.480 
38.230 
37.980 

92.89 
163.37 
114.49 
126.52 
139.40 

107.59 
118.03 
129.19 
141.22 
154.10 

60 
65 
70 
75 

80 

520.66 
525.66 
530.66 
535.66 
540.66 

517.93 
514.73 
511.52 
508.29 
505.05 

2.70 

2.48 
2.27 
2.09 
1.92 

.3697 
.4039 
.4401 
.4791 
.5205 

.0265 
.0266 
.0268 
.0270 
.0272 

37.736 
37.481 
37  .  230 
36.995 
36.751 

153.18 
167.92 
183.65 
200.42 

218.28 

167.88 
182.62 
198.35 
215.12 
232.98 

85 
90 
95 
100 
105 

545.66 
550.66 
555.66 
560.66 
565.66 

501.81 
498.55 
495.29 
492.01 

488  .  72 

1.77 
1.64 
1.51 
1.39 
1.289 

.5649 
.6120 
.6022 
.7153 

.7757 

.0273 
.0275 
.0277 
.0279 
.0281 

36.509 
36.258 
36.023 
35.778 

237.27 

251.97 

110 

570  .  66 

485  62 

1  203 

8312 

0283 

259.70 
275.79 

272.14 
293.49 

115 

120 

575.66 
580.66 

482.41 

478  .  79 

1.121 
1.061 

.8912 
.9608 

.0285 

.0287 

301  .  46 

316.16 

125 

585  66 

475  40 

9699 

1  0310 

0289 

325.72 

310.42 

130 

590.66 

472.11 

.9051 

1  .  1048 

.0291 

•  •  -  

352  MECHANICAL  REFRIGERATION-ENGINEERING 

The  ammonia-compressor  is  a  compression-pump,  and  may  be 
considered  as  such  in  every  sense  of  the  word,  but  it  must  be  a  better 
pump  than  those  which  are  more  common  in  the  steam-plant.  The 
object  of  this  pump  is  to  take  ammonia  gas  from  the  refrigerating 
portion  of  the  system,  and  compress  it  to  a  considerable  pressure  and 
discharge  the  compressed  gas  into  the  condenser.  The  latter  is  a 
series  of  pipes  over  which  water  is  kept  flowing  for  cooling,  and,  finally, 
for  the  liquefaction  of  the  gas.  The  ammonia,  on  being  liquefied 
in  the  condenser,  passes  on  to  the  ammonia-receiver,  which  is  a  vessel 
of  any  convenient  size  and  shape  adapted  to  hold  a  suitable  quantity 
of  the  liquid  and  from  which  a  considerable  quantity  may  be  with- 
drawn continuously  and  evaporated  in  the  refrigerating-pipes.  In  the 
latter,  sufficient  heat  is  absorbed  to  supply  the  latent  heat  required 
by  the  gas,  after  which  the  gas  returns  to  the  compressor. 

With  the  foregoing  brief  description  of  the  essentials  of  the  system, 
the  engineer  may  proceed  to  start  the  compressor  for  continuous 
work.  The  compressor  may  be  driven  by  a  steam-engine  or  electric 
motor,  and  in  some  cases  water-power  is  used  for  this  purpose.  When 
shutting  down  their  engines  or  stopping  the  compressor  for  any 
reason,  some  engineers  leave  the  discharge-  and  suction-valves  in  the 
ammonia  system  open,  as  they  were  during  the  time  the  machine 
was  running,  while  others  often  close  the  suction-  and  discharge- 
valves  and  sometimes  forget  to  open  them  before  trying  to  start. 
Do  not  make  this  mistake,  for  many  accidents  have  happened  because 
the  discharge-valve  was  closed  when  the  compressor  was  started. 

There  is  not  as  much  danger  in  leaving  the  suction-valve  closed, 
for  the  worst  that  could  happen  would  be  to  create  a  high  vacuum  on 
the  suction  side.  If  the  discharge-valve  happens  to  be  closed,  each 
stroke  of  the  compressor  will  add  to  the  pressure  in  the  discharge- 
pipe,  which  will  soon  run  up  to  a  dangerous  point.  The  careful 
engineer  will  keep  his  eye  on  the  pressure-gauge  while  starting  the 
compressor  and  until  he  is  assured  that  the  compressor  is  running 
at  the  proper  speed  and  that  there  is  a  free  escape  for  the  ammonia. 
Usually  there  are  no  cylinder-cocks  to  be  opened  previous  to  the 
starting  of  the  compressor  and  none  to  be  closed,  except  on  the  steam 
end.  There  is  little  chance  therefore  for  the  engineer  to  make  a  mis- 
take, provided  the  pressure-gauge  shows  that  the  pressure  is  within 
the  proper  limits. 


MECHANICAL  REFRIGERATION-ENGINEERING  353 

Forward  or  compressor  pressure  required  is  determined  in  nearly 
all  cases  by  the  temperature  and  amount  of  the  condensing  water. 
Further  information  on  this  point  may  be  obtained  by  examining  the 
temperatures  and  consequent  pressures  as  given  in  the  table,  where  it 
will  be  found  that  ammonia  under  a  pressure  of  200  pounds  to  the 
square  inch  has  a  temperature  of  about  100°  F.,  while  the  cooling 
water  may  have  a  temperature  of  only  50°.  The  boiling-point  of 
ammonia  under  200  pounds  pressure  with  a  temperature  of  100°, 
shows  that  the  temperature  of  the  compressed  gas  must  be  reduced 
below  100°  in  order  to  be  able  to  liquefy  it. 

There  is  a  difference  of  a  few  degrees  between  the  temperature  of  the 
gas  or  liquid  inside  the  pipe  and  the  temperature  that  will  be  obtained 
on  the  outside — that  is,  where  the  ammonia-pipes  in  the  condenser 
are  clean  and  free  from  scale,  mud,  and  slime.  The  difference  of 
temperature  inside  and  outside  the  pipes  will  range  from  5  to  8° 
under  usual  working  conditions.  With  unfavorable  conditions  the 
difference  in  temperature  may  be  almost  any  amount.  A  difference 
of  temperature  will  also  be  found  in  the  refrigerating-pipes,  and  this 
will  be  found  to  be  about  the  same  number  of  degrees  under  the 
same  conditions. 

With  a  gas-pressure  in  the  condenser  of  200  pounds  and  with 
water  at  50°  flowing  over  the  condenser-pipes,  the  best  conditions 
will  be  obtained  when  the  temperature  of  the  water  leaving  the  con- 
denser is  within  a  few  degrees  of  the  temperature  of  the  ammonia 
inside  the  pipes.  The  temperature  due  to  the  pressure  of  the  am- 
monia gas  in  the  condenser  is  always  a  few  degrees  higher  than  that 
due  to  the  boiling-point  of  liquid  ammonia  under  the  pressure  carried. 
This  difference  of  temperature  is  due  to  the  superheating  of  the 
ammonia  when  compressed  in  the  compressor,  which  will  vary  ac- 
cording to  the  conditions  of  operation  and  the  kind  of  compressor  used. 

Suction-pressure  on  the  system  is  nearly  always  a  few  pounds 
above  that  of  the  atmosphere,  although  it  is  sometimes  found  necessary 
to  reduce  this  pressure  below  that  of  the  atmosphere  for  special 
kinds  of  work.  For  economical  results  the  less  difference  between 
the  condenser-  and  suction-pressures  the  less  power  will  be  required 
to  operate  the  system.  For  a  given  amount  of  refrigeration  the 
suction-pressure  usually  is  regulated  by  the  lowest  temperature 
required  in  all  parts  of  the  system,  provided  the  proper  amount  of 


354 


MECHANICAL  REFRIGERATION-ENGINEERING 


piping  is  employed.  The  engineer  must  make  sufficient  allowance 
for  the  loss  of  temperature  by  transmission  through  the  pipes,  which, 
as  previously  mentioned,  may  amount  to  from  5  to  8°,  but  some- 
times may  reach  a  much  higher  figure.  Reference  to  the  table  of 
pressures  and  corresponding  temperatures  will  indicate  the  proper 
suction-pressure  for  the  lowest  temperature  it  may  be  required  to 
reach. 

When  considering  the  principles  of  operation  of  a  mechanical 
refrigerating-plant,  we  shall  see  that  the  effects  produced  are  all  due 
to  a  simple  exchange  of  heat,  for  when  we  compress  the  gas  we  squeeze 
out,  so  to  speak,  a  certain  portion  of  the  latent  heat,  and  the  gas 
being  under  pressure,  its  latent  heat  is  less  than  when  under  a  lower 
pressure.  The  latent  heat  taken  up  by  the  water  requires  a  much 


bumpiest  Apparatus 

Brine  Tank  or  Concealer  A. 


FIG.  328. — Diagram  illustrating  the  principles  of  refrigeration  by  ammonia. 

larger  quantity  of  water  for  condensing  purposes  than  that  due  merely 
to  the  difference  between  the  temperature  of  the  compressed  gas  and 
that  of  the  liquid  ammonia  under  this  pressure. 

Superheating  of  the  gas  is  due  to  the  latent  heat  set  free  by  the 
greater  density  of  the  compressed  gas,  and  it  is  the  removal  of  this 
latent  heat  which  gives  the  liquid  greater  capacity  for  absorbing 
heat,  and  as  heat-absorption  is  the  object  to  be  attained  the  ammonia 
should  not  be  fed  to  the  refrigerating  portion  any  faster  than  it  can 
absorb  heat.  Furthermore,  when  it  reenters  the  compressor  it  should 
be  all  gas,  except  in  cases  where  a  small  amount  of  liquid  is  permitted 
to  enter  the  compressor  for  purposes  which  will  be  explained  later. 


MECHANICAL  REFRIGERATION-ENGINEERING  355 

One  way  in  which  the  proper  pressure  on  the  suction  side  may 
be  determined  is  by  frost  covering  the  suction-pipes.  As  long  as 
there  is  frost  on  the  pipes  it  shows  that  there  is  still  unevaporated 
ammonia  in  the  pipe.  Some  engineers  do  not  appear  to  understand 
clearly  whether  it  is  the  ammonia  gas  or  the  liquid  ammonia  that 
absorbs  heat.  A  simple  test  will  determine  this  point  in  a  way  that 
will  render  clear  to  the  average  person  just  what^takes  place  in  the 
pipe  when  partly  rilled  with  ammonia.  It  will  also  demonstrate  the 
temperature  produced  on  the  outside  of  the  pipe.  Ammonia  gas  has 
little  effect  in  absorbing  heat,  because  the  gas  is  already  supplied 
with  nearly  the  full  quantity  of  latent  heat  required  to  keep  it  in  the 
gaseous  condition.  This  point  can  be  made  clear  by  taking  a  test- 
flask  or  a  common  tumbler  partly  filled  with  liquid  ammonia  and 
exposing  it  to  the  atmosphere.  As  heat  is  supplied  from  the  flask 
and  the  surrounding  atmosphere,  the  ammonia  will  begin  to  boil  to  a 
noticeable  degree,  which,  however,  will  continue  for  a  moment  only, 
for  the  contents  of  the  flask  soon  become  cooled  to  such  an  extent 
that  a  coating  of  frost  is  produced  on  the  surface  by  the  condensation 
of  moisture  from  the  atmosphere. 

Frost  thus  produced  will  increase  in  thickness  until  a  layer  is  ob- 
tained through  which  heat  can  pass  less  readily;  then  the  boiling  of 
the  ammonia  will  be  greatly  reduced,  and  only  small  bubbles  of  gas 
will  be  seen  rising  through  the  liquid  and  given  off  at  the  surface. 
The  level  of  the  liquid  ammonia  in  the  flask  is  marked  by  the  frost- 
line  on  the  outside,  no  frost  whatever  appearing  at  a  greater  height 
than  the  level,  except  perhaps  for  J  inch  or  so  where  the  warmer  gas 
is  in  contact  with  the  glass.  Air  on  the  outside  and  the  gaseous 
ammonia  on  the  inside  cause  the  frost  to  melt  and  form  a  thin  ring  of 
ice  or  a  mixture  of  ice  and  water  at  the  line  where  gas  and  liquid  meet. 
This  experiment  should  prove  conclusively  that  it  is  the  liquid  am- 
monia that  does  the  work  of  absorbing  heat  under  the  conditions 
noted,  in  which  case  ammonia  gas  under  pressure,  the  conditions  may 
be  considered  as  being  the  same  as  in  the  glass,  for  the  latent  heat 
in  the  ammonia  gas  at  the  suction-pressure  has  been  fully  supplied, 
and  the  gas  has  no  further  capacity  for  absorbing  heat.  Therefore 
the  liquid  ammonia  only  is  available  for  that  purpose.  Thus  we  can 
readily  understand  that  ammonia  passing  through  the  pipes  in  the 
refrigerating  system  remains  partly  in  the  liquid  state  as  long  as  there 


356  MECHANICAL  REFRIGERATION-ENGINEERING 

is  frost  on  the  pipes,  and  that  the  point  where  the  liquid  ceases  to 
exist  as  such  is  marked  by  the  absence  of  frost. 

The  amount  of  liquid  ammonia  to  be  supplied  to  the  refrigerating 
system  is  thus  determined  by  the  coating  of  frost  on  the  pipes,  since 
the  presence  of  frost  is  a  sure  indication  that  there  is  some  liquid 


FIG.  329. — Ammonia-compressor. 

ammonia  in  the  pipe  at  that  point,  while  the  absence  of  frost  indicates 
that  the  temperature  of  the  pipes  cannot  be  below  the  freezing-point. 
In  some  systems  frost  is  carried  back  to  the  compressor;  in  other 
systems  frosty  pipes  are  only  carried  inside  the  cooling-rooms.  It 
may  be  said,  regarding  the  presence  of  frost  on  the  pipes  and  the 
absence  of  it,  that  so  long  as  we  are  dealing  with  ammonia  gas  we 
have  only  the  specific  heat  of  the  gas  to  aid  us  in  obtaining  the  cooling 


MECHANICAL  REFRIGERATION-ENGINEERING 


357 


effect,  but  in  the  transformation  from  the  liquid  to  the  gaseous  state 
we  have  not  only  the  specific  heat  of  the  liquid  but  the  latent  heat  of 
the  ammonia.  The  specific  heat  would  not  pay  for  the  work  required 
in  compression,  for  the  latent  heat  is  what  is  most  important,  and  it 
may  be  considered  that  it  is  all  that  is  available  in  evaporation  of 
liquid  ammonia. 

It  is  well  known  by  all  engineers  that  the  compression  of  air  or 
gas  develops  a  large  amount  of  heat,  while  the  expansion  of  a  gas 
will  absorb  heat,  thus  producing  a  lower  temperature  of  the  surround- 
ings. It  is  also  well  known  that  the  evaporation  of  a  liquid,  which 
is  thus  transformed  into  a  gas,  will  absorb  heat,  and  that  the  amount  of 
heat  thus  absorbed  will  be  equivalent  to  the  latent  heat  of  the  gas 
at  the  pressure  under  which  it  is  generated. 

Fig.  329  illustrates  this  principle  for  operating  a  compressor.  A 
simple  non-condensing  automatic  engine  drives  a  crank-shaft  in  the 
usual  way,  but  a  vertical  connecting-rod  is  driven  by  the  same  crank- 
pin,  and  this  gives  motion  to  a  vertical  compressor,  as  shown.  A 
heavy  balance-wheel  on  the  same  shaft  provides  steady  motion  for  the 
moving  parts  by  absorbing  power  during  the  first  part  of  each  stroke 
and  giving  it  out  during  the  latter  part.  The  illustration  shows  a 


V 

*       Brine-Tank  or  Cong-ealer  A 


Compression 

Refrigerating 

Apparatus 


FIG.  330. — Three  stages  of  refrigeration. 

duplex  compressor.  One  cylinder  is  located  just  over  the  engine- 
crank,  while  another  crank  and  cylinder  are  placed  on  the  other  end 
of  the  shaft. 

In  Fig.  330  are  illustrated  the  three  principal  phases  or  stages  in 


'o 

G 

.2 

1 

I 
I 

.g 

3 

$ 


I 


5        §? 


MECHANICAL  REFRIGERATION-ENGINEERING 


359 


the  operation  of  refrigeration  by  the  ammonia  compression  system, 
although  in  a  complete  plant  there  are  many  adjuncts  for  special 
service,  such  as  oil-separators,  receiving-tanks,  filters,  and  brine-agi- 
tators, which  are  shown  in  the  full-page  cut,  Fig.  331. 

In  the  simple  round  of  ammonia-circulation,  it  starts  from  the 
compressor  under  a  high  pressure  and  temperature,  passing  to  a 
cooling-coil,  which  is  the  condenser,  where,  by  means  of  a  cold-water 
sprinkler,  the  gas  is  cooled  to  45°  or  50°  F.  At  that  temperature, 
under  the  high  pressure  the  gas  is  condensed 
to  its  liquid  state  and  passes  to  a  storage-tank, 
or  may  be  throttled  by  a  valve  to  maintain  a 
constant  pressure  on  the  liquid,  and,  by  allowing 
of  control  in  its  issue  to  the  refrigerating-coil, 
and  by  its  reevaporation  therein  under  a  low 
pressure,  to  absorb  the  heat  of  the  brine  or  air 
in  a  cold  chamber  that  is  required  for  vaporiz- 
ing the  liquid  ammonia  within  the  coils. 

Fig.  332  illustrates  the  De  La  Vergne  stand- 
ard double-acting  vertical  compressor,  the 
operation  of  which  may  be  explained  as  follows : 
Suppose  that  the  piston  is  ascending  with  a 
charge  of  gas  above  it.  As  the  space  holding 
this  gas  becomes  less  its  pressure  rises  until  it 
is  high  enough  to  overcome  that  carried  on  the 
discharge-pipe.  There  are  two  discharge- valves 
in  the  upper  part  of  this  machine,  a  full  view 
of  one  and  a  section  of  the  other  being  shown. 
These  rise  and  let  the  compressed  gas  out 
through  the  right-hand  passage  to  the  conden- 
ser. At  the  same  time  gas  under  light  pressure  is  drawn  in  through 
the  lower  suction-valve,  at  the  left  hand,  until  the  space  below 
the  piston  is  filled  with  it.  As  the  downward  stroke  is  made 
this  gas  is  compressed  until  the  pressure  is  high  enough  to  force 
it  out,  through  the  two  lower  discharge-valves  at  the  right,  to  the 
condenser. 

There  is  a  hollow  space  in  the  piston,  covered  by  two  valves 
opening  upward.  When  the  piston  has  nearly  reached  the  end  of 
its  downward  stroke  and  the  lower  valve  is  closed  by  the  piston, 


FIG.  332. — De  La  Vergne 
vertical  ammonia- 
cylinder. 


360 


MECHANICAL  REFRIGERATION-ENGINEERING 


the  pressure  is  sufficient  to  raise  the  valves  and  discharge  the  gas, 
through  the  higher  one  of  the  right-hand  discharge-valves,  to  the 
condenser. 

Fig.  333  shows  the  sectional  details  of  the  single-acting  com- 
pressor of  the  Frick  Company.  The  gas  at  suction-pressure  enters 
below  the  piston  from  the  right-hand  valve,  passing  through  a  light 
spring-balanced  valve  in  the  piston,  is  compressed  above  the  piston, 
and  is  discharged,  through  the  lifting  of  the  large  spring-held  valve, 
at  the  top  of  the  piston,  and  to  the  condenser. 

The  principal  feature  in  this  design  is  the  safety-head  or  discharge- 
valve,  which  allows  the  piston  to  touch  it  at  each  stroke,  thus  elimi- 
nating all  clearance  and  adding  its 
effect  to  the  efficiency  of  the  com- 
pressor. The  apparent  striking  of 
the  discharge-valve  at  the  moment 
of  the  passage  of  the  crank-centre, 
or  even  slightly  before  it,  can  do 
no  damage,  as  the  valve  is  lifted  at 
that  moment  and  falls  gently  upon 
the  piston-head  during  the  last  of 
the  discharge. 

Fig.  334  illustrates  a  section 
of  the  De  La  Vergne  horizontal 
double-acting  ammonia-compressor 
cylinder.  It  has  some  features  of 
safety  not  covered  in  many  gas-  or 
air-compressors.  This  cylinder  has 
as  small  clearance  as  possible,  in 
view  of  which  it  will  be  seen  that 
the  valves  must  be  as  near  the 
piston  as  practical,  in  order  to  make  the  clearance  small  and  produce 
an  economical  machine.  The  suet  ion- valves  are  above  the  cylinder 
in  this  case  and  the  discharge-valves  below  it;  consequently  if  any 
liquid  finds  its  way  into  the  cylinder  it  is  well  drained  out.  None  of 
the  valves  can  drop  into  the  cylinder  in  case  the  springs  break,  which 
is  an  important  consideration. 

In  all  double-acting  machines  the  piston-rod  stuffing-box  is  sub- 
jected to  the  full  compression-pressure,  which  may  be  over  200  pounds, 


FIG.  333. — Frick  Company  ammonia- 
cvlinder. 


MECHANICAL  REFRIGERATION-ENGINEERING 


361 


and  as  this  gas  is  of  a  penetrating  nature,  especially  when  under  such 
high  pressure,  it  is  sometimes  difficult  to  keep  a  stuffing-box  tight 


FIG.  334. — De  La  Vergne  horizontal  ammonia-cylinder. 

without  excessive  friction.  This  is  accomplished  here  by  the  use  of 
two  sets  of  packing-rings,  and  between  them  there  is  a  device  for 
oiling  the  rod,  which  is  plainly  shown. 


SURFACE-     AND     DOUBLE-PIPE     CONDENSERS 

The  Linde  surface-condensers  (a  portion  of  which  is  shown  in  Fig. 
335)  are  built  in  such  a  way  that  the  flanges  at  each  end  of  the  straight 
pipes,  when  screwed  together,  form  a  hollow  column,  which,  by 
means  of  special  flanges,  is  divided  into  different  compartments.  The 
warm  ammonia  gas,  when  discharged  into  the  top  of  one  of  the  col- 
umns, is  divided,  so  as  to  reduce  the  velocity,  and  then  passed  through 
three  pipes.  At  the  other  end  the  three  pipes  join,  and  the  gas,  after 
being  mixed,  is  again  divided  into  six  or  more  pipes,  so  as  to  still 
further  reduce  the  velocity  and  give  it  time  to  become  thoroughly 
cooled.  This  action  is  repeated  until  the  ammonia  is  delivered  at  the 
bottom  of  the  condenser  in  liquid  form.  By  reducing  the  velocity 
the  friction  also  is  reduced,  and  condensation  is  effected  in  a  shorter 
time.  The  pressure  also  is  considerably  reduced,  which  in  some 
cases  amounts  to  25  pounds. 

From  the  lower  part  of  the  condenser  the  liquid  ammonia  is  drawn 


362 


MECHANICAL  REFRIGERATION-ENGINEERING 


FIG.  335. — Surface-condenser. 

bottom  and  is  forced  upward 
through  the  smaller  inner  pipe. 
As  the  water  does  not  come  in 
contact  with  the  atmosphere, 
after  having  cooled  the  gas  it 
can  be  used  for  other  purposes. 
As  no  water  runs  over  the  out- 
side pipes,  no  tank  is  required 
to  collect  the  condensing  water, 
and  therefore  the  condenser  can 
be  placed  in  any  room,  pro- 
vided the  temperature  of  the 
room  is  not  too  high.  On  ac- 
count of  placing  one  pipe  with- 
in the  other  the  space  allowed 
for  the  ammonia  gas  is  small, 
and  consequently  the  amount 
of  gas  surrounding  the  water- 
pipes  is  also  small,  so  that  heat 
is  quickly  extracted.  This  is  an 


off  and  passed  through  a  sepa- 
rate upper  pipe,  where  it  is 
brought  in  contact  with  the  cold- 
est water  and  cooled  down  as 
near  as  possible  to  the  tempera- 
ture of  the  water. 

The  construction  of  the 
double-pipe  condenser,  Fig.  336, 
is  such  that  one  pipe  is  placed 
within  the  other,  which  pipes, 
at  each  end,  are  connected  by 
special  bends,  so  as  to  make  two 
separate  zigzag  sections  of  inner 
and  outer  pipes. 

Ammonia  gas  enters  at  the 
top  and  is  forced  downward 
through  the  large  outer  pipe, 
while  the  water  enters  at  the 


.AMMONIA   GAS  INLET 


FIG.  336. — Double-pipe  ammonia-condenser. 


MECHANICAL   REFRIGERATION-ENGINEERING  363 

advantage,  since  the  quicker  ammonia  gas  is  cooled  and  liquefied,  the 
lower  will  be  the  pressure,  and  less  power  is  required  to  drive  the  com- 
pressor. As  the  coldest  water  enters  at  the  lower  end  of  the  coil- 
section,  where  the  liquid  ammonia  collects,  a  thin  layer  of  liquid 
ammonia  is  quickly  reduced  to  the  temperature  of  the  coldest  water. 
The  surface-condenser  has  the  advantage  that  the  pipes  are  always 
open  for  inspection,  and  can  be  cleaned  and  painted  when  necessary, 
and  always  kept  in  good  condition.  With  a  double-pipe  condenser, 
where  the  water-pipe  is  inside,  they  cannot  be  so  readily  examined,  but 
special  provisions  are  made  for  cleaning  the  pipes.  In  certain  cases 
where  the  required  quantity  of  cooling  water  is  limited,  or  where  water 
is  metered  and  must  be  paid  for,  a  condenser  of  special  design  is  built 
with  the  object  of  saving  water.  With  these  condensers,  which  are 
called  evaporative  condensers,  the  quantity  of  cooling  water  is  reduced 
to  one-tenth  the  quantity  required  for  ordinary  condensers.  The 
latter  condensers,  on  account  of  their  special  construction,  are  some- 
what more  expensive  in  first  cost,  but  where  water  is  scarce  or  has 
to  be  paid  for  they  soon  pay  for  themselves. 

THE     DIAGRAM     OF      A  M  M  O  N  I  A  -  C  O  M  P  R  E  S  S  I  O  N 

The  specific  heat  of  anhydrous  ammonia  is  about  the  same  as  that 
of  water,  or,  more  exactly,  1.096  at  0°  F.,  and  decreases  with  the 
rise  in  temperature  at  the  rate  of  .0012  per  degree  F. 

The  latent  heat  of  vaporization  at  —40°  F.  is  579.6  thermal  units 
per  pound,  sustaining  a  pressure  of  10.7  pounds  per  square  inch.  Its 
latent  heat  decreases  gradually  with  increasing  temperature  and 
pressure,  and  at  100°  F.  is  491.5  thermal  units  per  pound,  and  sustain- 
ing a  pressure  of  215  pounds  per  square  inch. 

The  compression  of  its  vapor  follows  the  adiabatic  law  of  gases 
and  vapors,  subject  to  the  influence  of  the  walls  of  the  cylinder  in 
absorbing  the  heat  of  compression. 

Fig.  337  shows  a  diagram  of  the  compression-lines  for  ammonia 
vapor  between  the  return-pressure  of  20  pounds  and  discharge- 
pressure  of  150  pounds  per  square  inch.  The  adiabatic  line  is  repre- 
sented by  the  logarithmic  exponent  of  the  P  V  equation,  which  is 
1>297,  or  1>3  as  generally  expressed;  the  equation  in  which  the  P  V1-3  = 
PI  Vi1-3  represents  the  integration  of  the  curve. 


364 


MECHANICAL   REFRIGERATION-ENGINEERING 


It  will  be  seen  that  the  absorption  of  heat  by  the  cylinder- walls 
drops  the  line  of  compression  below  the  adiabatic  line,  and  thus 


ATMOSPHERIC  LINE 


VACUUM  LINE 


FIG.  337. — Diagram  of  ammonia-compression. 

contributes  to  the  efficiency  of  the  compressor,  and  also  shows  the 
volume  of  delivery  between  the  observed  temperatures. 


POINTERS     ON     THE     OPERATION     OF     AMMONIA 
COMPRESSION     SYSTEMS 

It  is  not  the  intention  of  the  author  to  go  very  deeply  into  the 
theory  of  mechanical  refrigeration,  as  the  practical  end  of  the  business 
is  where  trouble  is  generally  found;  but  it  is  absolutely  necessary 
for  the  engineer  to  have  the  right  foundation  on  which  to  base  his 
practice,  and  to  assist  in  this  a  few  definitions  and  rules  will  be  given. 

Mechanical  refrigeration  is  brought  about  by  an  exchange  of 
heat  between  two  bodies;  and  it  is  well  to  remember  that  whether  heat 
is  sensible  or  latent  it  is  never  destroyed,  but  simply  removed  or  ab- 
sorbed by  another  body  whose  temperature  is  lower  than  that  of  the 
body  from  which  heat  is  taken.  Heat  that  manifests  itself  by  means 
of  the  sense  of  feeling  or  by  the  aid  of  a  thermometer  is  called  sensible 
heat.  In  changing  a  solid  into  a  liquid,  or  a  liquid  into  a  gas,  a  certain 
amount  of  heat  is  required  to  effect  the  transformation,  and  this  is 
called  the  latent  heat. 

The  process  of  refrigeration  by  the  compression  system  is  divided 


MECHANICAL   REFRIGERATION-ENGINEERING  365 

into  three  stages,  compression,  condensation,  and  expansion.  The 
ammonia  gas  is  first  drawn  into  the  compressor  and  compressed  to 
approximately  150  pounds  per  square  inch.  During  compression 
the  latent  heat  of  the  gas,  which  in  this  case  is  the  amount  of  heat 
absorbed  in  its  transformation  from  a  liquid  into  a  gas,  is  given  up  in 
form  of  active  or  sensible  heat.  Some  compressors  have  a  water- 
jacket  cylinder  to  prevent  this  heat  from  doing  damage  by  destroying 
lubrication,  but  as  the  jacket  has  only  a  local  effect,  it  is  sometimes 
found  necessary  to  inject  oil  in  large  quantities,  and  this  generally 
causes  trouble  by  passing  the  oil-trap  in  the  form  of  a  vapor  and  coating 
the  condensing  system.  Some  compressors  are  so  arranged  that  a 
small  portion  of  the  liquid  ammonia  is  carried  back  to  the  machine 
and  converted  into  gas  during  the  compression  period,  and  that  the 
latent  heat  thus  absorbed  assists  in  keeping  the  temperature  of  com- 
pression down  to  a  point  where  water-jackets  are  not  necessary.  If 
the  temperature  can  be  kept  down  to  about  120  to  130°  F.  no  trouble 
will  be  experienced  from  that  source. 

When  gas  at  150  pounds  pressure  is  forced  into  the  condenser, 
the  cooling  water  running  over  the  pipes  absorbs  the  active  or  sensible 
heat  developed  during  compression,  thus  removing  the  heat  which 
was  necessary  to  keep  the  ammonia  in  a  gaseous  state,  and  again 
transforming  it  into  a  liquid  at  a  temperature  approximating  that  of 
the  condensing  water,  but  at  the  pressure  existing  in  the  condenser. 
The  liquid  ammonia  is  admitted  to  the  expansion-coils  through  a 
regulating-  or  expansion-valve  in  such  quantities  as  are  necessary 
for  the  work  on  hand.  In  these  coils,  owing  to  the  lower  pressure 
maintained,  the  liquid  ammonia  again  expands  into  a  gas,  and  during 
this  transformation  absorbs  practically  the  same  amount  of  heat 
from  surrounding  objects  that  it  gave  up  to  the  cold  water  in  the 
condenser. 

The  economical  operation  of  a  plant  of  this  kind  requires  two 
things,  viz.,  pure  ammonia,  as  the  boiling-point  of  ammonia  varies 
directly  in  relation  to  the  purity,  and  keeping  the  system  in  such  a 
condition  that  ammonia  will  not  be  lost  as  a  result  of  leaks.  This 
trouble  is  one  frequently  met  with.  The  compressor  runs  smoothly 
and  everything  seems  to  be  as  it  should,  but  perhaps  the  proper 
results  are  not  being  attained  in  the  pipe-lines.  Perhaps  direct- 
expansion  piping  does  not  frost  up  as  it  should  and  brine  tempera- 


366  MECHANICAL  REFRIGERATION-ENGINEERING 

tures  are  too  long  falling.  The  usual  trouble  is  the  lack  of  liquid 
ammonia  in  the  system,  or  some  obstruction  at  the  expansion-valve. 
If  there  is  sufficient  ammonia  the  gas  will  be  running  heavy  enough 
to  make  a  very  distinct  clicking  at  the  valves  in  the  compressor, 
while  with  a  lighter  gas  caused  by  a  lack  of  liquid  these  valves  will 
be  almost  if  not  entirely  noiseless.  If  the  trouble  is  at  the  expansion- 
valve  it  is  generally  easy  to  detect  it  by  opening  and  closing  the 
valve  several  turns  and  listening  to  the  passage  of  the  ammonia, 
for  if  the  valve  is  at  fault  the  sound  will  remain  the  same  at  all  posi- 
tions. 

Having  a  machine  too  small  for  the  work  will  also  make  a  poor 
showing  at  the  expansion-coils,  but  if  there  is  plenty  of  ammonia  in 
the  system,  trouble  from  this  cause  will  also  be  accompanied  by  a 
high  back  pressure,  as  the  ammonia  expands  to  a  gas  faster  than  the 
machine  can  take  care  of  the  gas,  and  in  consequence  the  back  pressure 
will  build  up  until  the  extra  pressure  in  the  expansion-coils  is  suffi- 
cient to  retard  the  inflow  of  liquid  ammonia  and  the  consequent 
evaporation.  If  the  expansion-valve  is  found  to  be  passing  gas,  or 
if  the  temperature  of  the  pipe  between  the  liquid-receiver  and  the 
expansion-valve  is  found  to  be  much  below  that  of  the  condensing 
water,  the  engineer  will  be  safe  in  assuming  that  the  supply  of  am- 
monia in  the  system  is  too  small.  The  condenser-coils  should  be 
kept  free  from  permanent  gases  by  the  use  of  a  gas-  or  purge-valve 
located  at  the  top  of  the  coils,  and  they  should  be  .kept  as  clean  as 
possible  at  all  times  so  that  the  entire  benefit  of  the  water  may  be 
derived. 

In  looking  for  leaks  in  the  system,  they  may  be  quite  easily  located 
by  making  long  sulphur  matches  out  of  pine  splinters  by  dipping 
them  in  melted  sulphur,  and,  after  lighting,  holding  one  of  them  close 
to  and  around  the  point  thought  to  be  leaking.  If  the  leak  is  there, 
the  sulphur  fumes  and  the  ammonia  fumes  will  combine  and  form  a 
dense  white  vapor.  This  is  also  a  good  point  to  remember  where  direct 
expansion  is  used  in  the  cold-storage  rooms,  as  in  case  of  a  break  or 
a  severe  leak  the  ammonia  gas  can  be  neutralized  by  this  method, 
merely  placing  a  pan  of  burning  sulphur  inside  the  room.  In  this  way 
work  can  be  started  much  sooner  than  would  be  possible,  unless  there 
is  some  good  means  of  ventilation,  which  as  a  general  thing  is  not 
provided.  A  good-sized  stream  of  water  from  a  hose  directed  on  a 


MECHANICAL   REFRIGERATION-ENGINEERING  367 

serious  break  in  an  ammonia-pipe  will  sometimes  enable  the  engineer 
to  get  to  the  stop-valve  and  close  it  before  the  whole  charge  of  am- 
monia is  lost.  A  common  source  of  small  leaks  is  the  piston-rod 
stuffing-box;  and  the  engineer  should  use  great  care  in  packing  this 
box,  because  a  leak  at  this  point  is  both  costly  and  disagreeable. 
The  packing  should  fit  the  stuffing-box  snugly,  and  be  cut  to  lengths 
so  that  the  ends  will  meet  but  not  overlap.  This- packing  should  be 
tight  enough  to  require  tapping  into  place  with  a  wooden  packing- 
stick  and  small  hammer. 

Coils  of  ammonia-condensers  usually  are  vertical  pipes  connected 
with  return-bends.  Should  a  leak  develop  near  the  centre  of  the 
coil,  the  quicker  remedy  is  to  cut  the  nearest  return-bend  with  a 
hack-saw  and  remove  the  two  pieces,  after  which  the  leaky  pipe 
may  be  attended  to  properly  and  the  joint  made  by  using  a  return- 
bend  made  in  two  or  three  parts  and  clamped  together  with  bolts. 
While  on  the  subject  of  pipe-joints  for  holding  ammonia,  several  kinds 
that  give  good  service  may  be  mentioned.  A  joint  may  be  made  by 
tinning  the  fitting  and  the  end  of  the  pipe  and  heating  them  hot  enough 
to  make  a  sweat-joint  when  screwed  together.  If  an  annular  space  is 
made  in  the  fitting  about  two  threads  deep,  and  if  after  making  the 
fitting  up  tight,  this  space  is  filled  with  solder  and  wiped  off,  it  makes 
an  excellent  joint,  but  it  is  slow,  costly  work  and  requires  careful  hand^ 
ling.  A  common  way  is  to  clean  the  threads  with  naphtha  or  gasolene, 
and  then  paint  them  with  a  pigment  made  of  glycerine  and  litharge. 
This  will  harden  in  a  short  time,  and  if  carefully  put  up  will  give 
excellent  results. 

In  making  pure  crystal  can  ice  perhaps  the  greatest  difficulty  the 
engineer  will  encounter  will  be  to  keep  it  clear  and  free  from  cores. 
Absolute  cleanliness  is  the  greatest  help  toward  attaining  this  end. 
The  red  core  is  caused  by  iron  oxide  from  the  steam-condenser  coils 
getting  past  the  filters,  which  is  something  that  can  be  prevented 
if  proper  care  is  taken.  The  boilers  should  be  kept  clean  along  with 
the  rest  of  the  plant,  as  they  are  the  source  of  the  distilled  water, 
and  some  little  water  is  apt  to  be  carried  over  with  the  steam.  This 
may  not  be  much,  but  if  the  boilers  are  dirty  it  will  often  show  in  the 
ice.  A  leak  in  the  steam-condenser  will  often  bring  in  enough  foreign 
matter  to  cause  discoloration  in  the  ice. 

If  the  temperatures  in  a  cold-storage  room  are  not  low  enough  and 


368  MECHANICAL   REFRIGERATION-ENGINEERING 

the  coils  are  not  frosted  to  the  ends,  evidently  the  first  thing  to  do 
is  to  find  out  why  they  cannot  be  made  to  carry  frost  throughout  their 
entire  length.  The  fact  that  a  direct-expansion  pipe  accumulates 
frost  indicates  simply  that  the  vapors  and  liquid  ammonia  passing 
through  it  are  at  a  temperature  sufficiently  low  to  congeal  the  moisture 
of  the  air  which  comes  in  contact  with  it.  So  long  as  there  is  un- 
evaporated  liquid  ammonia  in  contact  with  the  vapor,  the  latter  is 
said  to  be  saturated,  and  the  temperatures  corresponding  to  the 
different  back  pressures  can  be  readily  determined  by  reference  to  the 
table  XL  of  Properties  of  Saturated  Ammonia. 

If  there  is  liquid  ammonia  enough  at  the  expansion-valve,  frost 
can  be  carried  the  full  length  of  any  coil  and  clear  back  to  the  machine, 
if  desired,  at  a  back  pressure  of  25  pounds,  because  the  temperature  of 
saturated  gas  at  25  pounds  pressure  is  11.5°  F.,  which  is  20.5°  F. 
below  the  freezing-point  of  water.  That  a  coil  does  not  frost  to  the 
end  under  a  back  pressure  of  25  pounds,  indicates  that  either  there  is 
an  insufficient  supply  of  liquid  ammonia  at  the  expansion-valve,  or 
that  there  is  an  obstruction  which  prevents  a  sufficient  amount  of  it 
from  passing  the  expansion-valve.  An  obstructed  expansion-valve  is 
indicated  by  there  being  little  or  no  change  in  the  sound  of  the  passing 
liquid  when  the  valve  is  opened  several  turns.  Such  obstructions  can 
often  be  removed  by  the  sudden  opening  and  closing  of  the  expansion- 
valve. 

Scarcity  of  liquid  at  the  expansion-valve  can  usually  be  recognized 
by  an  interrupted  hissing  sound,  the  hissing  being  caused  by  the 
passage  of  gas  and  the  interruption  by  that  of  the  liquid,  maybe  due 
to  one  of  two  things,  viz.,  an  insufficient  charge  of  ammonia  or  too 
small  a  machine.  If  there  is  a  sufficiently  heavy  charge  of  ammonia 
in  the  system  and  the  machine  is  much  too  small,  there  will  be  no 
whistling  sound  heard  at  the  expansion-valve,  but  the  machine  not 
being  able  to  carry  away  the  vapors  of  ammonia  as  fast  as  they  are 
formed,  the  back  pressure  will  rise  higher  until  the  extra  pressure 
serves  to  retard  the  evaporation  to  such  an  extent  that  the  machine 
cannot  take  care  of  it.  It  must  also  be  remembered  that  as  the  back 
pressure  rises  the  number  of  pounds  of  ammonia  handled  by  the 
machine  at  a  given  pressure  increases,  because  of  the  fact  that  the 
weight  of  a  cubic  foot  of  gas  increases  directly  with  the  absolute 
pressure. 


J 

lUNlVfRSITYj 
J 

N^IJFORS^^ 

MECHANICAL   REFRIGERATION-ENGINEERING  369 

While  the  size  of  a  machine  cannot  well  be  increased,  its  capacity 
for  doing  work  may  sometimes  be  increased  by  improving  its  efficiency. 
Sometimes  low  efficiency  is  due  to  dirt,  which  acts  like  an  insulating 
material  on  the  condensers  and  prevents  the  free  radiation  of  heat; 
sometimes  to  insufficient  or  poorly  distributed  water  on  the  con- 
densers, and  sometimes  to  so-called  permanent  gases  within  the  con- 
densation. 

With  well-sprinkled  coils  of  ample  size  210  pounds  head-pressure 
is  certainly  too  high  for  59-degree  water,  and  the  trouble  is  liable 
to  be  due  to  any  of  the  three  causes  above  mentioned. 

Ammonia  as  ammonia  cannot  deteriorate  in  quality,  but  at  high 
temperatures,  and,  according  to  some  authorities,  more  or  less  at 
moderate  temperatures,  it  does  slowly  disassociate  into  its  component 
gases,  hydrogen  and  nitrogen.  These  gases,  sometimes  called  per- 
manent gases,  because  they  do  not  liquefy,  accumulate  in  the  con- 
denser, and,  occupying  the  space  that  should  be  open  to  the  ammonia, 
cut  down  the  cooling-surface  and  thereby  cause  an  abnormally  high 
head-pressure.  These  gases  should  be  purged  from  the  system 
through  a  pipe  or  rubber  hose,  one  end  of  which  is  connected  to  the 
purge-valve  on  the  top  of  the  condenser  and  the  other  immersed  in 
a  pail  of  water.  If  a  sharp,  cracking  sound  is  heard  and  no  bubbles 
rise  to  the  surface  of  the  water  when  the  purge-valve  is  slowly  opened 
it  indicates  that  the  gas  is  soluble  in  water  and  is  ammonia.  If,  how- 
ever, bubbles  rise  to  the  surface  of  the  water  the  gas  is  proved  to  be 
comparatively  insoluble  and  is  not  ammonia.  The  gases  should  be 
allowed  to  escape  through  the  purge-valve  into  the  water  until  no 
more  insoluble  gases  appear.  The  water  should  be  changed  every 
few  minutes,  to  keep  it  from  becoming  saturated  with  the  ammonia, 
under  which  condition  it  will  bubble  through  the  water  in  much  the 
same  way  as  the  permanent  gases  do,  and  may  lead  to  deception 
regarding  its  true  nature. 

There  should  be  enough  liquid  ammonia  in  the  liquid-receiver  at 
all  times,  so  that  no  gas  will  pass  the  expansion- valve.  The  latter 
condition  can  be  readily  recognized  by  the  temperature  of  the  liquid- 
line  between  the  receiver  and  the  expansion-valve.  It  should  be  re- 
membered that  the  temperature  of  the  liquid  ammonia  going  to  the 
expansion-valve  should  be  approximately  that  of  the  cooling  water 
leaving  the  condensers,  and  that  a  wide  variation  in  temperature 


370  MECHANICAL  REFRIGERATION-ENGINEERING 

either  way  from  that  point  would  indicate  an  insufficient  supply  of 
liquid. 

The  condenser-coils  should  be  kept  clean  and  well  covered  with 
water  at  all  times,  and  they  should  also  be  kept  purged  free  from 
permanent  gases. 

CHARGING    AND    STARTING    AN    AMMONIA-COMPRESSOR 

As  each  type  of  ammonia-compressor  has  its  own  individual 
features  of  construction,  each  particular  machine  will  require  special 
care  and  adjustment,  so  that  no  fixed  rules  can  be  laid  down  to  suit 
all  cases.  There  are,  however,  some  general  principles  which  are 
applicable  to  all  types  based  on  the  compression  system. 

Before  charging  an  empty  machine  with  anhydrous  ammonia  all 
air  must  first  be  carefully  expelled.  This  is  done  in  various  ways.  One 
method  often  used  is  to  pump  the  system  full  of  gaseous  ammonia  and 
shut  the  engine  down.  Allow  the  water  to  flow  in  the  condensers 
until  all  the  ammonia  in  the  system  is  condensed.  The  liquid  am- 
monia, being  heavier,  will  naturally  gravitate  to  the  bottom  of  the 
system.  A  valve  can  then  be  opened  at  the  highest  part  of  the  sys- 
tem, and  the  pressure  of  the  ammonia  will  force  the  air  out;  the 
presence  of  ammonia  gas  will  indicate  when  to  shut  the  valve.  The 
system  can  then  be  allowed  to  stand  another  six  or  twelve  hours,  and 
the  valve  again  opened.  If  there  is  any  air  remaining  in  the  system, 
it  will  be  driven  out  when  the  valve  is  again  opened. 

Before  charging  the  system  it  can  be  thoroughly  tested  by  working 
the  compressor  and  permitting  air  to  enter  at  the  suction  through  the 
special  valves  provided  for  that  purpose,  and  it  should  be  perfectly 
tight  at  200  or  250  pounds  pressure  per  square  inch,  and  should  be 
able  to  hold  that  pressure  without  loss.  While  testing  the  system 
under  air-pressure,  it  should  be  carefully  and  thoroughly  cleaned  of 
all  dirt  and  moisture  by  blowing  out. 

In  some  cases  it  is  impossible  to  eject  all  air  from  the  plant  by 
means  of  the  compressor;  therefore  it  is  advisable  to  insert  the  requisite 
charge  of  ammonia  gradually.  Sometimes  from  60  to  70  per  cent, 
of  the  full  charge  is  put  in,  and  the  air  remaining  in  the  system  is 
allowed  to  escape  through  the  purging-cocks  with  as  little  loss  of  gas . 
as  possible,  subsequently  inserting  an  additional  quantity  of  ammonia 


MECHANICAL  REFRIGERATION-ENGINEERING  371 

once  or  twice  a  day  until  all  the  air  has  been  displaced  and  the  complete 
charge  has  been  introduced. 

To  charge  the  machine  the  drum  of  anhydrous  ammonia  is  con- 
nected through  a  suitable  pipe  to  the  charging- valve.  The  machine 
should  be  run  at  a  slow  speed  when  sucking  the  ammonia  from  the 
tank,  with  the  discharge-  and  suction- valves  wide  open.  When  one 
of  the  tanks  is  emptied  the  charging-valve  is  closed  and  another  tank 
placed  in  position,  and  the  process  continued  until  the  machine  is 
sufficiently  charged  for  work,  when  the  charging-valve  can  be  closed 
and  the  main  expansion-valve  opened  and  regulated.  A  glass  gauge 
upon  the  liquid-receiver  will  show  when  the  latter  is  partially  filled, 
and  the  pressure-gauges,  as  well  as  the  gradual  cooling  of  the  brine 
in  the  refrigerator  and  the  expansion-pipe  being  covered  with  frost, 
will  indicate  when  a  sufficient  amount  to  start  working  has  been 
inserted. 

The  machine  having  been  started  and  the  regulating-valve  opened, 
the  temperature  of  the  delivery-pipe  should  be  carefully  noted,  and 
if  it  shows  a  tendency  to  heat,  then  the  regulating-valve  must 
be  opened  wider,  while  if  it  should  become  cold,  the  valve  must  be 
slightly  closed,  the  regulation  or  adjustment  thereof  being  continued 
until  the  temperature  of  the  pipe  is  the  same  as  the  cooling  water 
which  leaves  the  condenser.  If  the  charge  of  ammonia  is  insuffi- 
cient, the  delivery-pipe  will  become  heated  even  when  the  regulating- 
valve  is  wide  open. 

Among  the  signs  which  denote  the  healthy  working  of  the  plant, 
beside  the  fact  that  it  is  satisfactorily  performing  its  proper  refrigerat- 
ing duty,  are  the  vibration  of  the  pointers  of  the  pressure-  and  vacuum- 
gauges  (which  clearly  mark  every  stroke  of  the  piston),  the  frost  on  the 
exterior  of  the  ammonia-pipes  (the  liquid  ammonia  can  be  distinctly 
heard  passing  through  the  regulating- valve  in  a  continuous  stream), 
and  the  difference  in  temperatures  between  the  condenser  and  the 
cooling  water  and  the  refrigerator  and  the  brine. 


CHAPTER    XXI 

THE    ELEVATOR   AND    ITS   WORKING 

THE  modern  installation  of  elevator  service  has  greatly  increased 
the  care  and  responsibility  of  the  engineer,  to  whom  such  duties  are 
usually  assigned;  and  in  view  of  these  duties  this  chapter  will  be 
deemed  not  out  of  place,  for  not  only  the  often  complex  details  of  the 
elevator  but  also  those  of  the  steam-pump  or  the  electric  motor  are 
in  charge  of  the  engineer. 

The  direct-acting  steam-motors  for  elevators  are  peculiar  in  their 
design,  and  require  the  care  and  watchfulness  of  the  experienced 
engineer. 

AIR-COMPRESSORS 

The  air-compressor — so  much  in  use  in  operating  mining-machines, 
hoists,  conveyers,  and  air-locomotives,  and  for  generating  power 
for  transmission  for  a  variety  of  factory  and  operative  purposes — 
becomes  a  specialty  in  the  care  of  the  engineer  of  such  plants. 

Of  the  many  types  or  methods  of  operating  elevators  we  note  the 
following : 

The  direct-cable  elevator,  in  which  a  reversible  steam-engine 
winds  and  unwinds  the  rope-cable  on  a  drum;  the  car,  which  is  partly 
balanced  by  a  cable  and  counterweight,  with  the  stop-  and  reverse- 
valves  operated  by  a  lanyard,  over  which  the  car  runs.  The  early 
safety-devices  were  a  form  of  ratchet-stop  (shown  in  Fig.  338),  suc- 
ceeded by  friction-devices  and  speed-governors  of  many  patterns. 

Elevators  of  the  type  classed  as  hydraulic,  and  operated  by  water- 
pressure  from  a  roof-tank  or  a  pressure-tank  fed  by  a  steam-pump, 
are  still  in  use.  One  of  this  type  is  illustrated  in  Fig.  339,  and  consists 
of  a  cylinder  of  one-half  the  length  of  the  lift,  with  a  piston  and  double 
piston-rods  for  safety.  The  pressure  is  downward  on  the  piston, 
for  elevating  the  car.  A  travelling  sheave  with  the  end  of  the  car-cable 
fixed  at  the  top  gives  the  car  twice  the  run  of  the  piston.  An  auto- 
372 


THE  ELEVATOR  AND   ITS   WORKING 


373 


FIG.  338. — Elevator- 
stop. 


matic  stop  controls  the  run  of  the  car,  and  a  lanyard-cable  controls 
the  speed  by  throttling  the  circulating-pipe. 

A  very  compact  hydraulic-elevator  plant  is  detailed  in  Fig.  340, 
with  a  cylinder-capacity  for  a  gear  of  2  to  1  or  4  to  1,  as  desired.  Here 
the  pressure-tank  is  placed  over  the  discharge- 
tank,  with  the  steam-pump  alongside.  The  prin- 
ciple of  operation  is  contained  in  the  action^ 
of  the  pilot-  or  transfer- valve,  which  is  itself 
operated  by  a  cable-lanyard  passing  through  the 
car  and  over  a  wheel  at  the  top  of  the  shaft  and 
over  the  valve-wheel  seen  at  the  top  of  the  valve. 
When  the  car  is  at  the  top  of  the  lift,  the 
piston  is  at  the  bottom  of  the  cylinder,  with  the 
valve  closed  to  hold  the  car.  To  bring  the  car 
down,  the  valve  opens  the  port  of  the  transfer-  or  circulating-pipe, 
wrhen  the  weight  of  the  car  and  load  transfers  the  water  from  above 
the  piston  to  its  under  side,  the  velocity  of  transfer  being  regulated 
by  the  amount  of  opening  of  the  valve.  To  start  the  car  upward, 

the  valve  is  moved  past  the  stop- 
position  and  opens  the  exhaust-port 
between  the  bottom  of  the  cylinder 
and  the  open  tank,  when  the  pres- 
sure from  the  high-pressure  tank 
forces  the  piston  down  with  a  ve- 
locity regulated  by  the  amount  of 
opening  in  the  exhaust-port. 

The  duty  of  the  pump  is  to 
transfer  one  cylinder  full  of  water 
for  each  complete  lift  and  return  of 
the  car,  from  the  exhaust-tank  to 
the  high-pressure  tank,  in  which 
the  air  is  compressed  to  form  the 
pressure-cushion. 

Another  type  of  the  hydraulic 


FIG.  339. — Hydraulic  piston-elevator. 


system  is  the  multiple  effect  of  a 
pushing  or  pulling  piston  upon  a 
series  of  pulleys,  by  which  a  short  horizontal  or  vertical  cylinder  will 
produce  a  lift  of  many  times  the  traverse  of  the  piston,  or  plunger. 


374 


THE  ELEVATOR  AND  ITS  WORKING 


Fig.  341  illustrates  a  section  and  side  view  of  the  plunger  type,  in 
which  A  is  the  cylinder;  P,  the  plunger;  EI,  E2,  E3,  the  three  sheaves, 
which  have  their  duplicate  at  the  bottom  and  their  anchor-eye  for  the 
cable  at  K,  giving  a  lift  of  8  to  1;  H,  the  valve-chest,  with  the  three 
positions  of  the  lever  for  start,  stop,  and  reverse.  R  is  an  automatic 
stop  on  a  valve-rod  operated  by  the  arm  Q  on  the  sheave-frame. 


SHIP  tmnm'mrmn 


FIG.  340. — Pressure-tank  elevator-plant. 

The  high-lift  plunger-elevator  (illustrated  in  Fig.  342)  has  been  so 
perfected  in  its  operation  by  experience  with  the  failures  of  the  tele- 
scopic lifts  of  the  early  hydraulic  elevators  that  it  has  now  attained 
a  lift  of  280  feet  with  a  single  plunger  traversing  a  cylinder  extending 
to  a  depth  beneath  the  ground  floor  more  than  equal  to  the  lift.  These 
elevators  run  at  speeds  from  200  to  600  feet  per  minute;  they  carry  a 
counterweight  of  90  per  cent,  of  the  total  load,  and  use  a  water- 
pressure  of  185  pounds  per  square  inch. 


THE   ELEVATOR  AND   ITS   WORKING 


375 


The  elevators  in  the  Trinity 
Building,  New  York  City,  are  of 
this  type,  with  plungers  6J  inches 
diameter  and  with  an  upward  fric- 
tion of  500  pounds. 

The  total  weight  of  the  high-lift 
car,  plunger,  and  fixtures  is  8,460 
pounds;  full  load,  1,600  pounds; 
total,  10,060  pounds.  The  counter- 
balance is  7,900  pounds,  leaving 
2,660  pounds,  including  friction,  to 
be  lifted  by  6,000  pounds  water- 
pressure  under  the  piston — suffi- 
cient for  a  speed  of  from  400  to  600 
feet  per  minute. 

Valves  entirely  independent  of 
the  main  controlling-valve  are  pro- 
vided to  bring  the  car  to  a  gradual 
stop  at  each  end  of  its  travel.  Two 
cables,  one  operating  at  the  top  of 
the  run,  the  other  at  the  bottom 


FIG.  341. — Plunger  multiple  lift. 


Exhaust 
FIG.  342. — High-lift  plunger-elevator. 


376 


THE  ELEVATOR  AND  ITS   WORKING 


FIG.  343. — Three-way  valve  and  pilot-valves. 


of  the  run,  are  connected  with 
these  automatic  valves,  as 
shown  in  the  cut  (Fig.  342). 

The  overrun  of  the  sheaves 
on  the  stop-cables  causes  their 
shortening,  which  lifts  the 
weighted  valve-levers  and 
shuts  off  the  supply- valve  or 
exhaust-valve  at  the  top  or 
bottom  of  the  car-run. 

The  elevator  is  controlled 
by  a  lever  in  the  car,  and  the 
main  three-way  valve  is  oper- 
ated by  a  pilot-valve,  as  illus- 
trated in  Fig.  343.  In  this 
way  an  easy  and  perfect  con- 
trol of  the  car  is  secured. 

In  Fig.  344  are  illustrated 
the  pushing  plunger  type  and 
its  operation  as  connected  to 
the  passenger-car,  complete 
with  governor  and  automatic 
stop,  with  lever  and  double 
sheave,  on  the  valve-lanyard 
in  the  car  for  control. 

This  type  is  operated  by 
the  same  combination  of 
pump,  open  and  closed  tanks 
as  shown  in  Fig.  340. 


FIG.  344.— Hydraulic  elevator,  horizontal  plunger. 


THE  ELEVATOR  AND  ITS  WORKING 


377 


In  Fig.  345  is  shown  the  safety-governor  of  the  Otis  elevator,  by 
which  a  brake  is  applied  to  the  governor-cable  when  the  speed  of 
the  car  exceeds  the  rate  at  which  the  governor  is  adjusted. 

Its  action  is  independent  of  the  lifting-cables,  so  that  in  case  of 
a  breakage  of  the  cables  it  will  bring  into  action  the  car  safety-devices 
to  which  it  is  connected,  and  will  bring  the  car  to  a  safe  and  easy  stop. 
The  governor-cable  is  endless,  passing  over  the_  driving-sheave  of 
the  governor  and  a  weighted  sheave  at  the  bottom  of  the  shaft.  It 
has  a  spring-stop  connected  to  the  gravity  wedge  mechanism  under 
the  car;  it  arrests  its  descent  when 
excessive  speed  is  attained  from  any 
cause. 

Fig.  346  shows  the  mechanism  of 
the  governor-cable  connection  to  the 
gravity-wedge  device.  A  and  B  show 
the  cable  running  over  the  governor- 
sheave;  to  the  side  A  are  attached 
stops  and  a  helical  spring  to  ease  the 
contact  with  its  engaged  lever  on  a 
sudden  change  of  speed.  The  lever 
operates  the  arm  of  a  rock-shaft  that 
extends  to  the  wedge-levers  on  each 
side  of  the  car. 

In  Fig.  347  is  represented  the 
action  of  the  gravity-wedge  safety- 
device  of  the  Otis  Company.  It  is 
best  described  in  their  own  words, 
which  follow: 

"  Under  the  car  is  a  heavy  hard- 
wood safety-plank,  on  each  end  of 

which  is  an  iron  adjustable  jaw,  enclosing  the  guide  on  the  guide-post. 
In  this  jaw  is  an  iron  wedge,  withheld  from  contact  with  the  guide 
in  regular  duty.  Under  the  wedge  is  a  rocker-arm,  or  equalizing-bar, 
with  one  of  the  lifting-cables  attached  independently  at  each  extremity. 
The  four  lifting-cables,  after  being  thus  attached,  pass  over  a  wrought- 
iron  girdle  at  the  top  of  the  car.  Each  cable  carries  an  equal  strain, 
and  the  breaking  of  any  one  cable  puts  the  load  on  the  other  cables, 
which  throws  the  rocker  out  of  the  horizontal  position,  and  forces  the 


FIG.  345. — Otis  automatic  governor. 


378 


THE  ELEVATOR  AND  ITS  WORKING 


FIG.  346. — Automatic  governor  controlled  safety-device. 


wedges  on  both  sides 
instantly  and  immov- 
ably between  the  iron 
jaws  of  the  safety- 
plank  and  the  side  of 
the  guides,  stopping 
the  car.  It  may  be 
raised  to  any  position 
by  the  unbroken  ca- 
bles, though  it  cannot 
be  lowered  until  a  new 
cable  is  put  on." 

A  is  the  elevator 
car-guide;  B,  safety- 
wedge;  C,  safety- 
wedge  shoe;  D,  ad- 
j  ustable  gib ;  E,  safety- 
wedge  back  spring; 
F,  F,  shackle-rods  on 


ends  of  cables;  G,  equalizing-bar;  H,  lever  to  lift  the  wedge;  I,  I,  set- 
screws  on  the  equalizing-bar  for 
adjusting  the  lever  H  to  lift  the 
wedge,  by  either  movement  of  the 
equalizing-bar,  from  the  breaking 
or  stretching  of  any  one  of  the 
cables. 

In  Fig.  348  is  shown  a  section 
of  the  Otis  Company's  vertical  hy- 
draulic cylinder,  circulating-pipe, 
valves,  and  valve-gear.  The  operat- 
ing-valve is  balanced  and  moved 
by  a  rack-stem  and  a  pinion  on  the 
shaft  of  the  sheave  carrying  the  car- 
lanyard.  Pressure  for  operating  is 
always  full  in  the  cylinder  above 
the  piston  and  in  the  circulating- 
pipe. 

The  valve,  as  shown  in  the  cut,   FIG.  347. — Gravity-wedge  safety-device. 


REFERENCES   TO   NUMBERED  PARTS 


1.  Travelling-sheave. 

2  Travelling-sheave  bushing. 

3  Travelling-sheave  pin. 

4.  Travelling-sheave  guard. 

5.  Travelling-sheave  strap. 

6.  Oil-cup. 

7.  Piston-rod  cross-head. 

8.  Stuffing-boxes. 

9.  Air-cock. 

10.  Drip-pipe. 

1 1 .  Curb  on  top  head  of  cylinder. 

12.  Piston-rods. 

13.  Cylinder. 

14.  Circulating-pipe. 

15.  Piston^ 

16.  Top   foltower. 

17.  Bottom  follower. 

18.  Piston  air-valve. 

19.  Piston-cup. 

20.  t-inch  square  rubber  packing. 

21 .  Set-screws  for  starting  top  follower 

when  removing  it  to  pack. 

22.  Cylinder-legs. 

23.  Drain  from  bottom  of  cylinder. 

24.  Water-chest. 

25.  Relief-valve,    to    relieve    ram    of 

water  when  the  valve  is  sud- 
denly closed  during  the  ascent 
of  car. 

26.  Valve-chamber. 

27.  Valve-plunger,    consisting  of:    A. 

Rack-follower;  B.  Valve-stem; 
C.  Top  to  valve  piston-cup;  D. 
Bottom  to  valve  piston-cup;  E. 
Spider;  F.  Valve-cup  packings. 

28.  Valve-rack. 

29.  Valve-rack  shoe. 

30.  Valve-pinion  shaft. 

31.  Valve-cap. 

32.  Valve-glands  on  pinion-shaft. 

33.  Valve-sheave. 

34.  Check-valve. 


FIG.  348. — Section  of  hydraulic-elevator  cylinder  and  valves. 


380 


THE  ELEVATOR  AND  ITS  WORKING 


is  at  "  stop  "  for  the  car;  lowering  it  opens  communication  between 
the  upper  and  lower  sections  of  the  cylinder,  and  the  car  descends  by 
its  own  weight  and  by  the  transfer  of  the  water  from  above  to  below 
the  piston.  By  raising  the  valve  the  water  beneath  the  piston  dis- 
charges, and  the  higher  pressure  on  the  upper  side  of  the  piston  sends 
the  car  upward. 

One  of  the  later  innovations  in  the  elevator  line  has  been  brought 
out  in  the  ramp,  or  escalator,  a  contrivance  which  affords  a  convenient 
way  of  getting  upstairs.  One  of  the  earlier  devices  is  shown  in 


FIG.  349.— The  ramp. 

Fig.  349,  with  sections  of  the  upper  and  lower  ends  of  the  ramp  with 
'the  driving-gear.  A  dynamo  and  a  transmission  device  drive  the 
upper  drum  and  guards  at  a  mean  speed  of  20  inches  per  second. 

The  system  comprises  an  endless  web  formed  of  bars  of  wood  which 
are  provided  with  rollers  that  are  formed  of  a  material  called  "  hema- 
cite  "  and  that  run  upon  rails.  The  returning  half  is  suspended  from 
a  rail  lodged  in  the  lower  chord  of  the  principal  girder.  This  arrange- 
ment of  chains  with  detachable  links  permits  of  doing  away  with 
stretchers. 


THE   ELEVATOR  AND  ITS   WORKING 


381 


The  jointed  web  is  actuated  by  a  chain  of  which  each  link  corre- 
sponds to  one  of  the  bars  of  wood.  This  passes  at  the  upper  part  over 
an  indented  wheel  actuated  by  the  electric  motor,  with  the  interposition 
of  a  shaft  with  a  ratchet  to  prevent  any  return  in  an  opposite  direction. 


FIG.  350.— The  step-escalator. 

The  jointed  bars  are  provided  with  rubber  projections  for  the 
purpose  of  giving  the  feet  a  firm  hold.  These  projections,  which  are 
arranged  in  longitudinal  bands,  make  their  exit  at  the  lower  part 
and  disappear  at  the  upper  between  the  teeth  of  metallic  combs 
designed  to  take  up  and  set  down  the  passengers  without  jerks.  The 
guards  consist  also  of  endless  chains  covered  with  rubber  and  cloth. 
Each  link  of  the  chain  slides 
in  a  groove  that  prevents 
any  lateral  displacement. 

A  perspective  view  of  the 
lower  end  of  the  ramp  in  the 
lower  section  of  the  cut  shows 
the  jointed  web,  sprocket- 
drums,  and  hand-rail. 

In  Fig.  350  is  illustrated 
the  newest  type  of  escalator, 
brought  out  by  the  Otis 
Company,  and  in  use  on  the 
Sixth  Avenue  Elevated  Railroad  and  at  the  Macy  department  store 
in  New  York  City.  It  will  be  seen  that  in  this  type  the  passengers 
step  onto  the  escalator  on  an  even  moving  floor  that  rises  into  steps 
at  the  incline,  which  again  form  an  even  floor  at  the  top  for  a  sufficient 


FIG.  351. — Worm-gear  elevator. 


382 


THE   ELEVATOR  AND   ITS  WORKING 


distance  to  step  off  without  trouble  or  danger.  The  hand-rail  travels 
at  the  same  rate  as  the  steps.  The  capacity  ranges  from  4,000  to 
6,000  persons  per  hour. 

Many  direct-cable  elevators  are  driven  through  worm-gear  which 
has  its  own  drawbacks  from  wear  and  cutting  of  the  gear.  For  safety 
in  this  respect  the  double  worm-gear  is  in  use,  which  reduces  the  fric- 
tion, serves  the  purpose  of  balancing  the  thrust  of  the  driving-shaft, 
and  is  also  a  means  of  safety  from  breakage  of  teeth.  The  worms 
have  right-and-left-hand  threads.  The  Sprague  type  of  electric-driven 
elevator  is  illustrated  in  Fig.  351. 


THE      MASON      ELEVATOR      PUMP-PRESSURE 
REGULATOR 

This  regulator,  which  is  illustrated  in  Fig.  352,  is  designed  for  the 
larger  sizes  of  steam-pumps  operating  hydraulic  elevators.  The  im- 
portant feature  in  this  machine  is  that  it  operates  on  the  slightest 

change  of  pressure,  opening 
and  closing  the  steam-valve 
to  its  fullest  extent  prompt- 
ly and  with  certainty. 

Referring  to  the  section- 
al view,  Fig.  353,  the  opera- 
tion is  as  follows:  Steam 
from  the  boiler  enters  the 
regulator  at  the  inlet,  and 
passes  through  the  main 
valve  into  the  pump,  which 
continues  in  motion  until 
the  required  water-pressure 
is  obtained  in  the  elevator 
system,  which  acts,  through 
a  J-inch  pipe  connected  at 
A,  upon  the  diaphragm  B. 
This  diaphragm  is  raised  by 
the  excess  water-pressure, 
and  carries  with  it  the 
FIG.  352. — Pump-pressure  regulator.  weighted  lever,  opening  the 


THE   ELEVATOR  AND   ITS  WORKING 


383 


auxiliary  valve  D,  and  admitting  the  water-pressure  from  the  con- 
nection E  to  the  top  of  the  piston,  at  the  same  time  opening  the 
exhaust-ports  under  the  piston,  thus  allowing  the  water  under  the  pis- 
ton to  escape  into  the  drip- 
pipe,  thereby  pushing  the 
piston  down,  which  closes 
the  steam-valve  and  stops 
the  pump. 

As  soon  as  the  pressure 
in  the  system  is  slightly  re- 
duced, the  lever,  on  account 
of  the  reduced  pressure  un- 
der the  diaphragm,  is  forced 
down  by  the  weight,  carry- 
ing with  it  the  auxiliary 
valve,  thus  opening  the 
exhaust  to  the  top  of  the 
piston,  and  at  the  same 
time  admitting  the  water- 
pressure  under  the  piston, 
•which  is  now  forced  up 
and  opens  the  steam-valve, 
again  starting  the  pump. 

The  main  balanced  valve 


FIG.  353. — Section  of  pump-pressure  regulator. 


and  the  controlling-valve  are  connected  by  an  outside  yoke,  as  are 
also  the  auxiliary  valve  D  and  the  lever,  as  shown  in  Fig.  352. 


AIR-COMPRESSORS      AND      COMPRESSED      AIR 

The  steam  end  of  an  air-compressor  is  essentially  the  same,  in  all  its 
details,  as  that  of  other  steam-engines,  as  explained  in  previous  chap- 
ters of  this  work.  The  air  end,  and  its  action  and  operation,  come 
within  the  province  of  the  engineer,  and  require  some  consideration. 
In  many  places  the  distribution  and  use  of  compressed  air  also 
require  some  knowledge  on  the  part  of  the  engineer  of  its  properties 
and  action.  For  details  of  the  uses  and  work  of  compressed  air  for  all 
purposes,  the  author  recommends  reference  to  his  large  work  on 


384 


THE  ELEVATOR  AND  ITS  WORKING 


"  Compressed  Air/'  published  by  the  N.  W.  Henley  Publishing  Com- 
pany, New  York  City. 

Compressed  air  is  not  only  used  for  running  local  motors,  hoists, 
and  rock-drills,  but  is  largely  in  use  for  refrigeration  in  the  marine  and 


FIG.  354. — Diagram  of  compression  and  expansion  of  air. 

the  naval  service.    The  compressed-air  brake  is  at  the  fore  hi  railway 
service. 

By  compression  and  expansion  air  obeys  the  laws  of  thermody- 
namics, becoming  hot  by  compression  and  cooling  by  expansion. 
For  an  assumed  compression  and  expansion  without  change  of  tem- 
perature—  isothermal— 
its  volume  and  pressure 
are  in  exact  inverse  pro- 
portion,   but   in   actual 
practice  in  the  compres- 
sor and  motor  the  lines 
of  pressure  and  expan- 
sion,   as   shown    on   an 
indicator  -  diagram,    are 
adiabatic    to   meet   the 
conditions   of   tempera- 
FIG.  355. — Two-stage  compression.  ture. 


THE  ELEVATOR  AND  ITS  WORKING 


385 


FIG.  356. — Bennett  air-compressor. 


In  the  diagram  (Fig.  354)  are  shown  the  theoretical  curves  due  to 
compression  and  expansion  where  there  is  no  transfer  of  heat  to  or  from 
the  walls  of  the  cylinder.  The  figures  along  the  margin  of  the  curves 
show  the  change  of  volume  from  the  isothermal  line.  In  actual 
practice  the  compression- 
volumes  are  less,  and  the 
expansion-volumes  are  some- 
what greater,  than  shown  by 
the  figures. 

The  mean  pressure  due  to 
compression  and  expansion, 
as  taken  by  an  indicator,  can 
be  figured  in  the  same  manner  as  with  the  steam-card  (see  Indicator, 
Chapter  XIII),  and  needs  no  further  explanation.  Full  details  of  the 
theory,  practice,  and  work  of  compressed  air  are  given  in  the  work  on 
"  Compressed  Air  and  Its  Uses"  by  the  author. 

The  effect  of  compressing  air  in  compound  or  by  two  stages  is 

shown  in  Fig.  355,  and  for  high 
pressures  a  three-stage  com- 
pression shows  much  economy 
in  the  power  used  for  compres- 
sion. 

In  the  two-stage  diagram 
it  may  be  seen  that  the  lower  curve  is  that  of  the  isothermal  up  to  80 
pounds  per  square  inch,  while  the  upper  curve  shows  the  increased 
volume  due  to  compounding  with  an  intercooler  to  shrink  the  volume 
before  it  enters  the  second  cylinder.  In  this  way  the  economy  in 
power  by  compound  compression  up  to  100  pounds  is  about  15  per 
cent.,  and  increases  with  higher  pressures. 


FIG.  357. — Clayton  compressor. 


FIG.  358. — Corliss  air-compressor. 


386 


THE  ELEVATOR  AND  ITS   WORKING 


The  accompanying  illustrations  are  those  of  some  of  the  models 
and  details  of  compressors  in  use. 


FIG.  360. — Ingersoll-Sergeant  cylinder. 


FIG.  359. — Duplex  tandem  air-compressor. 

In  Fig.  356  is  shown  an  elevation  of  the  Bennett  air-compressor, 
with  direct  piston-connection,  cross-head,  and  outside  connecting- 
rods  to  the  crank-pins  in  the  fly-wheels.  The  eccentric  on  the  shaft  at 

the  rear  of  the  steam-cylinder 
is  linked  to  a  vertical  lever 
and  valve-rod. 

In  Fig.  357  is  shown  the 
elevation  of  an  air-compressor 
of  the  Clayton  type,  in  which 
the  cylinders  are  placed  at 
each  end  of  the  bed  frame, 
and  with  yoked  piston-rod 
connection  and  with  the  crank  and  connecting-rod  within  the  yoke. 

The  direct-connected  tandem  system,  with  a  Corliss  steam-cylinder 
and  centrifugal  governor,  is 
shown  in  Fig.  358.  It  is  a  type 
of  air-compressor  now  rapidly 
increasing  in  economy  and  use- 
fulness by  tandem  compound- 
ing and  cross  -  compounding, 
and  is  in  use  in  large  plants. 

An  example  of  the  duplex 
tandem  type  of  air-compressor 
is  shown  in  the  plan  (Fig. 
359).  In  this  type  the  steam  FIG.  361.— Vertical  lift-valve  cylinder. 


THE  ELEVATOR  AND  ITS  WORKING 


387 


end  is  provided  with  a  throttling-governor  and  riding-cutoff  for  each 
cylinder. 

The  air-cylinders  are  of  the  Ingersoll-Sergeant  pattern,  set  on  a 
sole-plate  and  fastened  by  rods  to  the  steam-cylinders.  The  piston- 
rods  are  connected  by  couplings,  and  the  air-supply  is  regulated  by 
a  governor. 


FIG.  362. — Vertical  four-stage  air-compressor.  • 

Fig.  360  shows  the  cylinder,  piston,  and  valves  of  the  Ingersoll- 
Sergeant  pattern.  It  has  a  through  hollow  piston-rod,  into  which  the 
air  is  drawn  to  feed  the  hollow  piston  and  cylinder  through  the  annular 
valves,  one  of  which  is  shown  at  G.  These  valves  open  and  close  by 
their  momentum,  and  are  free  from  obstructive  pressure  against  the 
incoming  air. 

Fig.  361  illustrates  a  section  of  an  air -cylinder,  with  vertical  lift- 


FIG.  363. — Reynolds-Corliss  blowing-engine. 

Steeple  type,  condensing;  long  cross-head  connections  to  piston-rods  and  crank- 
rods.  The  air-cylinder  has  mechanically  operated  valves.  Built  by  the  Allis- 
Chalmers  Company  tor  blast-furnaces,  smelters,  and  Bessemer  work. 


THE  ELEVATOR  AND  ITS  WORKING  389 

valves  controlled  by  springs,  a  solid  piston,  and  with  cylinder-heads 
water- jacketed. 

In  Fig.  362  is  shown  an  end-view  sketch  of  the  largest  high-pressure 
air-compressor  ever  built.  The  steam-power  of  the  compressor  is 
derived  from  a  duplex  vertical  cross-compound  engine  with  Rey- 
nolds-Corliss valve-gear.  With  steam-pressure  of  150  pounds  and  40 
revolutions  per  minute,  it  is  equal  to  1,000  horse-power.  Directly 
beneath  each  pair  of  steam-cylinders  is  placed  a  pair  of  air-cylinders, 
tandem,  and  connected  to  the  steam-cylinder  cross-heads  by  a  yoke- 
frame.  The  steam-cylinders  are  32-  and  68-inch  by  60-inch  stroke. 
The  air-cylinders  are  46-,  24-,  14-,  and  6-inch  by  60-inch  stroke;  they 
are  tandem  in  pairs  and  single-acting.  The  approximate  capacity  at 
the  above  speed  is  2,269  cubic  feet  of  free  air  per  minute.  The  pressure 
in  the  first  cooler  is  40  pounds;  second  cooler,  180  pounds;  third  cooler, 
850  pounds,  and  in  the  after-cooler  2,300  pounds..  It  was  built  by  the 
Allis-Chalmers  and  Ingersoll-Sergeant  companies  for  the  Metropolitan 
Railway  Company,  New  York  City,  for  charging  the  car-tanks  and 
operating  air-power  cars. 

There  is  much  acumen  required  in  an  engineer  operating  a  large 
air-plant  that  is  not  usual  in  the  experience  of  the  young  engineer,  so 
that  a  special  study  should  be  made  of  the  written  or  personal  instruc- 
tions given  by  the  builders  of  such  plants,  as  their  construction  is  as 
variable  in  detail  as  that  of  steam-plants. 

A  type  of  the  massive  engines  used  for  supplying  air  under 
pressure  to  the  blast-furnaces  of  the  iron  industry  is  shown  in  Fig. 
363.  The  man  on  the  floor  represents  a  comparative  proportion  for 
the  size  of  this  colossal  blowing-engine. 


CHAPTER    XXII 

THE    COST    OF    POWER-ECONOMY 

THE  subject  of  the  cost  of  power  for  various  mechanical  uses 
and  for  electric  power  and  lighting  has  been  a  theme  of  engineering 
papers  and  of  discussion  in  technical  journals  for  many  years  past, 
with  varying  results  depending  upon  the  varying  conditions  in  the 
cost  of  material  and  labor. 

We  append  an  abstract  from  a  communication  of  Mr.  William  0. 
Webber,  of  Boston,  Mass.,  containing  his  experience  in  the  matter  of 
the  cost  of  a  steam-plant  and  the  operating  cost  of  plants  of  various 
sizes  and  types.  The  cost  of  land  and  buildings  will  probably  make 
a  material  difference  in  estimating  the  total  cost  of  power,  and  for  the 
annual  cost  of  operating,  the  insurance,  interest,  and  repairs  should 
enter  into  the  items  of  expense. 

The  following  table  shows  the  estimated  cost  of  a  plant  in  the 
Eastern  States  for  a  60-brake  horse-power  : 

TABLE  XLI.  —  COST  OF  A  60-BRAKE  HORSE-POWER  PLANT 

Land  for  engine  and  boiler-room  ..................  $2,500  .  00 

Buildings  for  engine  and  boiler-room  ...............  2,500.00 

Chimney  .......................................  1,200.00 

80  horse-power  boiler  ............................  $790  .  00 

Ash-pan  for  boiler  (below  high  tide-level)  ...........  120.00 

Blow-off  of  sink  .................................  31  .00 

Boiler-  and  engine-settings  .......................  1,282.00 

Damper-regulator  ...............................  75  .  00 

Injector-tank  ...................................  10.00 

Water-meter  ....................................  60.00 

Piping  .........................................  22.13 

Pump  ..........................................  146.50 

Feed-water  heater  ...............................  70  .  40 

Pipe-covering.  .  .  .  .  -  70,76 


Engine  12x30  ..................................  1,065.00 

Pan  for  engine-flywheel  ...........................  72.00 

Steam-separator  .................................  60  .  00 

Oil-separator  ....................................  41  .80 

Piping,  freight,  and  cartage  .......................  1,026  .41 

Shafting  in  place  ......  .  .........................  550.00 

Belting  in  place  .................................  285.00 


$11,977.99 

11  977  99 

-  =  $199.61,  or  say  $111  per  brake  horse-power  for  the  machinery  alone. 
60 

390 


THE  COST  OF  POWER-ECONOMY 


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392 


THE  COST  OF   POWER-ECONOMY 


The  annual  cost  per  brake  horse-power,  of  operating  the  ordinary 
types  of  steam-plants  under  200  horse-power  may  be  stated  as  follows : 


TABLE  XLIIL — OPERATING  EXPENSES. 


Average 
horse-power. 

Cost  of  coal  per 
ton,  2,240  pounds. 

Total  cost 
per  annum. 

Remarks. 

182 

$3.50 

$57.59 

No  land  or  building  costs. 

133 

3.25 

60.00 

"      "     cost. 

100 

3.50 

65.00 

"      "or  building  costs. 

97 

4.45 

86.80 

All  costs  included. 

75 

2.90 

92.40 

No  land  or  building  costs. 

50 

4.75 

111.05 

tt            ft           it              il                          K 

20 

4.45 

133.50 

All  costs  included. 

3.5 


3.0 


o 

X 

5:2.0 


1.5 


1.0 


EFFECT  OF  LOAD-FACTOR  ON  THE  COST  OF  POWER 

For  an  electrical  system  the  great  desideratum  is  a  high  load- 
factor  with  consequent  greatest  return  on  investment,  load-factor 
being  the  ratio  of  average  to  maximum  load.  All  the  factors  of  expense 

included  in  cost  of  power  to  the 
consumer  are  then  operating  at 
maximum  economy,  and  cost 
of  power  is  at  a  minimum. 

In  Fig.  364  is  a  diagram 
showing  the  total  operating  ex- 
penses, labor  repairs  and  sup- 
plies, and  fixed  charges  in 
curves  representing  the  cost  in 
cents  per  kilowatt  hour  for  full- 
load  and  under-load  conditions. 
In  Fig.  365  is  also  a  diagram 
for  the  same  conditions  in  a 


non-condensing  plant,  in  which 
it  may  be  observed  that  the  two 

lower  curves  are  the  same  as 
F,G.  364.-^>perating  expenses  of  a  900-kilo-    ^         fa  ^     m    &nd  ^    ^ 
watt  condensing  steam-plant. 

uppermost  curve  represents  the 
increased  cost  due  to  the  steam  end  of  the  plant. 

Lighting  of  residences  and  offices  produces  a  peak  in  the  late  after- 


,9       .8 


.7       .6       .5       .4 
LOAD  FACTOR 


THE  COST  OF  POWER-ECONOMY 


393 


3.5 


3.0 


2'5 


2.0 


noon  and  evening,  with  but  little  load  the  remainder  of  the  twenty- 
four  hours;  consequently  the  average  load  on  the  plant  with  lighting 
only  is  small  and  the  load-factor  low.  A  commercial  motor-load  in 
connection  with  lighting  will  increase  the  average  load  even  though 
causing  a  greater  peak.  The  addition  of  a  street-railway  load  still 
further  increases  the  day  load, 
but  in  consequence  of  the  heavy- 
demand  load  during  the  rush- 
hours,  when  the  public  is  going 
to  and  from  business,  which  oc- 
curs at  the  peak  of  the  lighting- 
load,  the  peak-load  on  the  plant 
is  greatly  increased.  This  heavy 
peak,  with  but  a  small  average 
load  over  the  twenty-four  hours, 
produces  a  low  load-factor,  as  a  '  }-° 
portion  of  the  machinery  is  shut 
down  the  greater  part  of  the 
time. 

In  the  cost  of  power  to  the 
consumer  various  expenses  are 
involved,  viz.,  management,  dis- 
tribution, and  production. 

For  a  given  system  with  given  peak-load  the  cost  of  management 
is  practically  constant,  no  matter  what  the  load-factor. 

Cost  of  distribution  is  constant  with  various  load-factors  in  so  far 
as  the  fixed  charges  and  maintenance  are  concerned.  The  losses 
in  distribution,  however,  vary,  these  consisting  of  losses  in  lines,  trans- 
formers if  alternating  current  is  used,  meters,  losses  in  grounds,  and 
losses  from  theft  of  current. 

As  to  cost  of  production,  the  higher  the  load-factor  the  greater  is 
the  amount  of  power  produced,  the  longer  does  the  apparatus  operate 
at  best  efficiency,  the  lower  the  ratio  of  fixed  charges  to  total  operating 
expenses,  and  consequently  the  lower  the  cost  of  power  per  unit. 


.7       .6        .5        .4 
LOAD  FACTOR 


FIG.  365. — Operating  expenses  of  a  900- 
kilowatt  non-condensing  steam-plant. 


394  THE  COST  OF  POWER-ECONOMY 


ECONOMICAL   SUGGESTIONS   IN   THE 

GENERATION  AND  USE  OF  STEAM 

FOR   POWER   PURPOSES 

Although  it  is  difficult  to  give  any  general  information  on  this 
subject  which  will  be  of  use  or  interest  in  the  great  variety  of  particular 
cases,  it  may  be  of  some  interest,  and  possibly  of  assistance  to  those 
who  are  managing  or  operating  power-plants,  to  discuss  some  of 
the  principles  upon  which  economy  in  the  use  of  steam  depends. 

Beginning  with  the  boiler,  which  is  the  first  step  in  the  production 
of  power  from  fuel,  it  may  be  laid  down  as  a  good  rule  that  it  is  more 
economical  to  use  boilers  of  reasonably  large  size  than  to  subdivide 
into  a  larger  number  of  small  units.  The  length  and  area  of  grate 
that  can  be  conveniently  fired  or  kept  evenly  covered  with  coal  are, 
perhaps,  the  limiting  features,  if  hand-firing  is  to  be  used.  Working 
from  this  rule,  a  grate  should  not  be  over  7  feet  long  or  more  than  5 
feet  wide,  which  would  give  35  square  feet  of  grate-surface.  The 
quantity  of  coal  that  may  be  burned  on  such  a  grate  varies  widely 
with  the  kind  of  fuel  and  strength  of  draught.  Using  bituminous 
slack  coal  of  fair  quality,  with  good  natural  draught  or  moderate- 
induced  draught,  it  should  be  possible  to  burn  25  pounds  of  coal 
per  square  foot  of  grate  per  hour,  or  875  pounds  of  coal  per  hour  for 
35  square  feet,  and  if  this  coal  will  evaporate  say  8  pounds  of  water  per 
pound  of  coal,  the  boiler,  if  constructed  with  heating-surface  in  proper 
proportion,  would  evaporate  7,000  pounds  of  water  per  hour,  which 
would  be  equal  to  a  little  over  200  standard  boiler  horse-power.  In 
order  to  give  good  economy,  the  boiler  should  have  from  2,000  to  2,400 
square  feet  of  heating-surface  to  evaporate  this  quantity  of  water 
economically.  The  return  tubular  boiler,  on  account  of  the  amount  of 
tube-surface  in  proportion  to  the  direct  surface  exposed  to  the  fire, 
should  have  not  less  than  12  square  feet  per  horse-power;  the  water- 
tube  type,  from  10  to  11,  and  the  internally  fired  type,  which  has  a 
larger  amount  of  direct  heating-surface  in  the  furnace  and  tubes  than 
either  of  the  others,  should  have  9  to  10.  If  the  grate-surface  is  larger 
than  that  described,  probably  the  grate  will  not  be  evenly  covered 
with  coal,  or  the  fire  will  be  dead  in  spots,  so  that  too  much  cold 
air  will  pass  through. 


THE  COST  OF  POWER-ECONOMY  395 

The  economy  in  burning  fuel  is  a  matter  requiring  great  skill 
and  experience,  and  depends  entirely  upon  the  evenness,  thickness, 
and  condition  of  the  fire,  which  controls  entirely  the  air-supply  and, 
therefore,  the  perfection  or  imperfection  of  the  combustion. 

It  is  too  often  the  case  that  the  demands  for  increased  horse-power 
are  met  by  grate-surface  too  large  in  proportion  to  the  heating-sur- 
face of  the  boiler  or  forced  draught,  and  too  little  attention  is  given 
to  careful  firing,  with  heating-  and  grate-surfaces  in  proper  propor- 
tion to  give  best  economy,  and  frequently  a  great  deal  of  money  is 
spent  in  obtaining  high-class  engines  and  condensers,  whereas  the 
principal  loss  is  in  the  boiler  and  fire-room. 

The  question  is  often  asked  whether  in  case  of  installing  a  certain 
horse-power  of  boilers,  say  300  horse-power,  it  would  be  more  econom- 
ical to  have  three  boilers  of  100  horse-power  each  or  two  boilers  of 
150  horse-power  each.  We  would  advise  to  have  the  two  larger  units, 
as  it  will  always  be  found  that  the  larger  boilers  have  less  radiation, 
less  air-leakage,  and  better  combustion  than  a  corresponding  horse- 
power in  small  units.  If  it  is  necessary  to  have  a  spare  unit  for  cleaning, 
let  there  be  another  one  provided  of  the  same  size. 

In  regard  to  the  pressure  to  be  carried,  it  is  well  known  that  a 
high  pressure  gives  a  greater  amount  of  expansion  and  better  economy 
in  proportion  to  the  fuel  burned.  Even  with  simple  engines  in  which 
it  is  not  possible  to  obtain  the  full  advantage  of  expansion,  the  high 
pressure  of  steam,  which  is  drier  and  contains  a  larger  number  of 
heat-units  in  proportion  to  the  volume,  gives  the  best  results.  Every 
boiler  should  be  designed  for  not  less  than  150  pounds  pressure  per 
square  inch.  Even  if  it  is  not  possible  to  utilize  the  full  pressure,  the 
boiler  will  be  stronger,  last  longer,  and  be  a  better  investment  in  the 
long  run.  In  this  respect  the  water-tube,  boiler,  or  some  form  of 
internally  fired  boiler  in  which  the  shell-plates  are  not  exposed  to  the 
high  temperature  of  the  furnace,  is  certainly  safer  than  the  horizontal 
return  tubular  boiler,  because  for  large  units  intended  to  carry  high 
pressure  the  shell-plates  and  seams  must  be  of  considerable  thickness, 
which,  being  directly  exposed  to  the  hottest  part  of  the  fire,  are  liable 
to  give  trouble,  especially  if  there  be  any  scale  or  sediment  in  the  water 
which  may  settle  on  the  bottom  directly  over  the  fire. 

As  to  the  economy  of  various  types  of  boilers,  experience  shows 
that  all  of  the  standard  types — horizontal  return  tubular,  water- tube, 


396  THE  COST  OF  POWER-ECONOMY 

or  internally  fired — if  they  are  designed  with  proper  proportions  of 
heating-  and  grate-surface,  give  about  the  same  evaporation  per 
pound  of  coal,  provided  they  are  in  good  condition  and  clean  both  on 
the  fire-  and  on  the  water-surface.  While  the  externally  fired  boilers, 
either  of  the  return  tubular  or  the  water-tube  type,  are  said  to  have 
some  advantage  in  combustion,  on  account  of  the  heat  of  the  brick 
furnace,  they  are  subject  to  losses  which  are  more  serious  in  the  way 
of  air-leakage  in  the  setting  and  radiation. 

The  repairs  and  cost  of  keeping  up  brick  furnaces  are  considerable, 
and  as  a  result  of  deterioration  there  is  more  or  less  air-leakage  through 
the  brickwork  going  on  constantly.  In  this  respect  the  internally 
fired  boiler  has  a  great  advantage  over  return  tubular  or  water-tube 
boilers  with  brick  furnaces,  as  it  will  be  just  as  efficient  after  continued 
use  as  when  first  started. 

In  any  type  of  boiler  it  is  of  great  importance  to  keep  the  tubes 
and  other  surfaces  free  of  soot  and  scale.  Otherwise  a  large  loss  may 
be  sustained.  It  is  a  mistake  to  depend  entirely  on  the  steam-blower 
or  tube-cleaner,  which  only  removes  the  loose  soot,  a  scraper  being 
necessary  for  occasional  use  to  free  the  hard  scale;  otherwise  it  will  in 
time  accumulate  on  the  fire-surfaces.  It  is  necessary  to  point  out  that 
scale,  or,  worse  still,  oil  on  the  inside  of  a  boiler  may  be  a  source  of 
great  loss,  experience  having  proved  that  even  a  thin  film  of  oil  will 
so  prevent  the  transfer  of  heat  that  the  plates  or  tubes  will  be  burned 
in  a  short  time.  Nothing  but  pure  water  should  be  used  for  making 
steam,  and  the  practice  of  making  the  boiler  do  duty  as  a  water- 
purifier  as  well  as  a  steam-generator  cannot  be  too  strongly  condemned. 
If  the  owners  of  steam-plants  could  realize  that  a  very  small  deposit 
of  soot  on  the  outside  and  scale  on  the  inside  mean  a  loss  of  from  10 
to  20  per  cent,  of  the  total  fuel-consumption,  they  would  be  con- 
vinced that  it  would  be  much  cheaper  to  spend  money  in  purifying 
apparatus,  so  that  the  scale  or  sediment  will  be  removed  before  the 
water  is  fed  to  the  boiler. 

The  next  step  to  be  considered  is  the  heating  of  the  feed- water. 
This  may  be  accomplished  in  two  or  three  ways:  first,  by  means  of 
the  exhaust-steam,  which,  coming  from  a  non-condensing  engine,  is 
capable  of  heating  the  feed-water  to  212°  F.  and  of  saving  say  12  to 
15  per  cent,  as  compared  with  feeding  cold  water.  For  large  plants 
where  it  would  be  advisable  to  use  induced  draught  to  make  up  for  the 


THE  COST  OF  POWER-ECONOMY  397 

loss  in  temperature  of  the  chimney-gases,  which  produce  the  draught, 
it  will  undoubtedly  pay  to  use  an  economizer;  but  as  this  apparatus  is 
expensive  both  in  first  cost  and  in  up-keep,  the  amount  saved  in  utiliz- 
ing the  waste  gases  from  a  small  plant  would  probably  not  offset  the 
outlay.  The  closed  type  of  feed-water  heater  is  about  as  efficient  as 
the  open  type,  provided  the  water  is  pure,  and  it  avoids  trouble  from 
pumping  hot  water,  but  the  open  type  is  frequently  made  use  of  to 
assist  in  purifying  the  water  and,  if  properly  managed,  may  give  good 
service  in  that  respect.  For  condensing-engines  a  primary  heater 
of  the  closed  type  may  be  installed  between  the  engine  and  condenser, 
which  will  help  to  condense  the  steam  and  heat  the  feed-water  to  a 
low  temperature — say  130  to  140°  F.  A  secondary  heater,  either 
of  the  closed  or  the  open  type,  may  be  used  to  heat  the  feed-water  to 
a  still  higher  temperature,  say  212°  F.,  by  the  use  of  the  exhaust  from 
the  feed-  and  air-pumps,  which  exhaust  cannot  be  used  more  profitably 
than  in  this  way,  as  all  the  heat  is  returned  to  the  boiler. 

In  regard  to  the  type  of  engine  used  for  the  plants,  if  the  size  of  the 
plant  is  sufficient,  and  the  work  comparatively  steady,  the  highest 
possible  results  may  be  obtained  from  compound  condensing-engines 
using  the  highest  possible  pressure  of  steam,  but  under  other  conditions, 
such  as  variable  load  or  low  pressure  of  steam,  it  may  be  quite  possible 
that  the  simple  engine  will  give  better  results  and  cost  less  for  repairs. 
With  low  steam-pressure,  non-condensing,  there  is  certainly  nothing 
better  or  more  economical  than  a  single-cylinder  Corliss  engine  where 
it  can  be  installed  to  advantage.  In  the  case  of  direct-driven  electric 
units  of  small  size,  it  is  necessary  to  use  high-  or  medium-speed  engines, 
both  on  account  of  the  loss  in  friction  that  would  result  if  counter- 
shaft and  belting  are  used  and  because  the  higher-speed  machines  will 
give  the  best  regulation.  For  small  units  up  to  say  75  or  even  100 
horse-power,  there  is  nothing  better  than  the  modern  high-speed 
automatic  engine,  provided  it  is  of  good  design,  not  overloaded,  and 
not  overspeeded. 

As  illustrating  the  slight  wear  of  high-speed  engines  under  favorable 
conditions,  a  Robb- Armstrong  engine  of  12-inch  stroke,  which  has 
been  running  at  275  revolutions  per  minute  for  electric  lighting  for 
twelve  or  fourteen  years,  shows  only  about  two-thousandths  of  an 
inch  wear  of  the  journals  and  six-thousandths  of  an  inch  wear  of  the 
shaft-bearings. 


398  THE  COST  OF  POWER-ECONOMY 

Unfortunately,  this  class  of  engine  is  so  frequently  overloaded 
and  overspeeded  that  it  gives  poor  results  and  gets  a  bad  name,  whereas 
the  Corliss  slow-speed  type  of  engine  is  limited  both  in  the  matter  of 
speed  and  horse-power,  because  the  cut-off  of  the  single-eccentric  type 
will  not  go  much  beyond  half-stroke,  and  in  that  way  the  engine  is 
saved  from  overloading  and  abuse,  and  this  is,  perhaps,  one  of  its 
many  advantages.  A  compound  engine  is  not  suited  to  low  pressure 
or  irregular  loads,  and  the  extra  cylinder  and  complication  of  parts 
are  a  great  objection  under  such  conditions.  When  a  condenser  is 
used,  even  with  low  pressure  and  somewhat  irregular  loads,  it  may 
be  employed  to  advantage,  whereas  with  high  pressure,  say  from  125 
to  150  pounds  or  over,  the  non-condensing  compound  will  give  the 
best  results,  unless  the  load  is  very  irregular  and  running  to  light  loads 
a  large  part  of  the  time. 

The  question  is  sometimes  asked  whether  it  pays  to  reduce  the  pres- 
sure when  the  load  is  light.  From  experience,  we  do  not  believe  it 
pays  to  reduce  the  pressure  on  the  boiler,  excepting  in  very  extreme 
cases,  but  if  it  can  be  done  by  throttling  before  the  steam  reaches  the 
cylinder  of  the  engine,  it  would  be  an  advantage,  because  this  retains 
the  heat-units  due  to  the  higher  pressure  in  the  steam  and  the  throttling 
has  a  slight  superheating  effect. 

Another  source  of  considerable  loss  in  the  operation  of  steam- 
plants,  particularly  large  ones,  are  the  insufficient  size  of  piping  (caus- 
ing the  pressure  to  be  reduced  between  the  boiler  and  engine) ,  and  im- 
perfect drainage,  which  is  an  enemy  both  to  economy  and  to  the  life  of 
the  engine.  In  many  of  the  newer  plants  it  has  been  found  a  great 
advantage  to  install  receivers  to  equalize  the  pressure  and  to  collect 
the  water  before  it  reaches  the  engine. 

In  general  it  may  be  said  that  the  principal  cause  for  loss  in  steam- 
plants  is  the  use  of  engines  which  are  overloaded  or  unsuited  to  the 
conditions  of  work,  undersized,  or  which  have  badly  arranged  steam- 
and  exhaust-pipes.  Other  frequent  causes  are  the  imperfect  condition 
and  poor  operation  of  the  boilers.  In  many  plants  exhaust-steam, 
which  might  be  utilized  for  heating,  is  wasted,  and  in  others,  where  the 
exhaust-steam  is  utilized  for  heating,  power  is  wasted  by  excessive 
back  pressure.  The  most  economical  use  that  exhaust-steam  can  be 
put  to  is  for  heating,  because  thereby  all  the  latent  heat-units  are 
made  use  of,  but  it  should  be  done  without  back  pressure  on  the  engine, 


THE  COST  OF  POWER-ECONOMY  399 

by  means  of  a  vacuum  system  to  draw  the  steam  and  water  through 
the  heating-pipes;  otherwise  there  will  be  a  loss  both  of  fuel  and  of 
power,  due  to  the  engine  working  under  imperfect  conditions. 

The  system  in  general  use  for  heating  by  exhaust-steam  is  by 
means  of  coils  of  pipe  around  the  walls  or  overhead  in  factories  and 
mills  and  by  radiators  in  offices  and  private  rooms. 

If  the  space  to  be  heated  is  not  excessively  large,  the  back  pres- 
sure on  the  engine  should  not  exceed  2  or  3  pounds  per  square  inch, 
and  may  not  exceed  ^  pound  with  the  proper-sized  exhaust-pipe  and 
coil-connections. 

The  most  serious  trouble  from  back  pressure  in  an  exhaust  heat- 
ing-plant has  been  remedied  by  enlarging  the  area  of  the  exhaust- 
pipe  and  of  all  the  pipe-connections  to  the  coils,  so  that  the  inlet  of 
each  coil  is  as  large  as  or  larger  than  the  total  area  in  each  of  the 
radiating-coils,  resulting  in  the  reduction  of  the  back  pressure  from 
4  pounds  to  J  pound  per  square  inch. 


CHAPTER     XXIII 

THE   ENGINEER   AND   HIS   DUTIES 

WE  cannot  here  enter  into  a  description  of  the  innumerable  details 
and  intricacies  involved  in  the  proper  care  of  a  steam-plant,  such 
details  and  conditions  having  been  very  fully  illustrated  and  described 
throughout  the  foregoing  chapters  of  this  work.  The  minor  details  and 
the  knowledge  required  for  operating  a  steam  plant  and  for  detecting 
or  obviating  the  troubles  and  defects  constantly  arising  therein  are 
fully  explained  in  the  question-and-answer  form  in  the  many  books  on 
this  subject,  such  as  "  Combustion  of  Coal "  by  Barr,  and  "  Engine- 
Runners'  Catechism  "  and  "  Steam-Engine  Catechism  "  by  Grimshaw 
— most  interesting  books  for  students  and  young  engineers.  Their 
study  often  affords  hints  useful  to  older  heads,  so  that  every  engineer, 
on  taking  charge,  should  be  thoroughly  posted  on  the  requirements  of 
his  profession  in  proportion  to  the  extent  of  the  duties  assigned  to  him. 

If  all  the  duties  devolve  upon  one  person,  as  in  small  plants,  the 
operating  details,  through  all  the  steps  from  the  coal-heaver  to  the 
expert  steam-user,  should  be  at  his  command,  and  if  in  charge  of  a 
large  plant,  where  firemen,  water-tenders,  oilmen,  cleaners,  and 
machinists  in  repair-work  are  employed,  his  knowledge  of  the  require- 
ments of  all  detail  work  in  the  construction  of  the  plant  should  not 
only  be  of  the  expert  kind,  but  should  also  involve  a  large  experience 
in  the  whole  range  of  construction,  its  theory  and  practice,  in  steam- 
engineering.  If  an  electrical-generating  and  transmission  plant  is  in 
connection  with  a  power-plant,  he  should  be  also  an  electrical  expert 
that  he  may  readily  meet  the  contingencies  that  may  occur  in  any 
part  of  a  complex  power-installation. 

The  license  system  is  doing  much  for  the  education  of  engineers 
in  the  line  of  their  duty,  as  its  requirements  impose  an  effort  in  study 
that  would  otherwise  be  neglected. 

License  is  now  required  in  the  States  of  Massachusetts,  New  York, 
Ohio,  Illinois,  Wisconsin,  Missouri,  Minnesota,  Kansas,  Montana,  and 
other  States.  Municipal  license  is  required  in  many  of  the  large  cities. 
400 


THE  ENGINEER  AND  HIS   DUTIES  401 


KNOCKING  AND  OTHER  NOISES  IN  THE  ENGINE 

The  causes  of  knocking  or  other  noises  in  a  steam-engine  are 
anxieties  to  the  careful  engineer  from  their  numerous  locations  and 
signs  of  possible  danger.  They  may  be  generally  traced  by  the  ear,  or 
by  the  feeling  of  the  hand  or  fingers  in  contact  with  different  parts 
where  possibly  loose  joints  may  occur,  and  in  obscure  cases  by  a  small 
stick  of  hard  wood  placed  between  the  suspected  point  and  the  fingers 
or  teeth. 

Some  of  these  causes  may  be  enumerated,  commencing  with  the 
cylinder-head.  Water  in  the  cylinder  gives  a  peculiar  sound — a  rush 
and  a  blow — while  the  contact  of  solid  pieces  gives  a  click  or  thump 
the  character  of  which  a  little  experience  soon  reveals.  Looseness  in 
the  piston-rings ;  looseness  in  the  follower ;  rattling  of  nuts,  set-screws, 
or  springs  used  to  set  out  the  packing-rings,  by  being  cast  adrift  in 
the  chambers  of  the  spider  section  of  the  piston,  produce  a  constant 
click  at  every  stroke.  Other  causes  of  noise  are  looseness  of  the  rod 
in  the  piston  through  faulty  fastening;  looseness  of  the  end  of  the 
valve-rod  in  the  valve-connection  in  the  steam-chest  or  in  any  of  its 
joints,  direct  or  through  a  rocker-arm;  looseness  in  the  cross-head 
boxes  and  bearings,  piston-rod  key,  or  lock-nut.  Oval  bearings,  bound 
brasses,  and  side- thrust  should  be  examined,  particularly  the  last- 
named  at  the  crank-pin.  Main  journals  on  crank-end  of  shafts  may 
wear  and  have  a  thrust-jar.  Looseness  in  the  side-bearings  of  the  fly- 
wheel key  and  a  loose  joint  in  the  made-up  parts  of  a  fly-wheel  have 
sometimes  been  a  mystery  to  find.  Squeaking  anywhere  shows  the 
want  of  oil. 


DON  TS  FOR  ENGINEERS  AND  FIREMEN 

Don't  forget  to  look  at  the  water-gauge  or  to  try  the  gauge-cocks 
the  first  thing  in  the  morning. 

Don't  forget  to  open  the  drip-cocks  before  opening  the  throttle, 
which  should  only  be  just  started  from  its  seat  to  allow  the  cylinder 
to  warm  up  and  discharge  water. 

Don't  neglect  to  start  the  blow-off  every  morning,  before  pulling 
forward  the  banked  fire,  to  clean  out  any  sediment  that  may  have 


402  THE  ENGINEER  AND  HIS   DUTIES 

accumulated  in  the  blow-off  pipe  from  the  use  of  muddy  feed-water. 
Once  a  week  will  suffice  for  good  water;  and 

Don't  forget  to  blow  off  boilers,  surface  and  bottom,  if  so  arranged, 
at  stated  times,  to  suit  the  nature  of  the  water  in  use. 

Don't  allow  steam-traps  on  the  cylinder  or  cylinders  of  one  engine 
to  be  connected  in  any  way  to  the  steam-trap  or  discharge-pipe  of  any 
other  engine,  thereby  causing  water  to  be  drawn  back  into  a  cylinder 
when  the  engine  is  stopped.  Such  neglect  has  caused  a  wrecked 
engine. 

Don't  forget  to  lift  the  safety-valve  off  its  seat  at  least  once  every 
day,  nor  neglect  to  rig  a  lanyard  from  the  end  of  the  lever  to  a  con- 
venient place  for  this  purpose. 

Don't  neglect  to  provide  means  for  quickly  closing  the  water- 
gauge  valves  when  the  glass  breaks,  if  they  are  not  automatic. 

Don't  forget  your  regular  times  for  firing  and  for  cleaning  fires, 
and  don't  allow  holes  to  burn  in  the  fire-bed. 

Don't  let  the  ashes  accumulate  under  the  grate — choking  burns 
the  bars;  have  stated  times  for  cleaning. 

Don't  forget  to  look  at  the  water-gauge  or  to  try  the  gauge-cocks 
often,  and  don 't  fail  to  regulate  the  running  speed  of  the  boiler-pump 
or  injector  to  suit  the  requirement  of  an  even  water-level.  A  constant 
feed  is  best. 

Don't  forget  to  regulate  the  dampers  and  doors  exactly  to  produce 
an  even  rate  of  combustion;  if  automatic  dampers  are  in  use,  they 
should  be  often  examined. 

Don't  neglect  to  blow  out  the  steam-  or  water-gauge  connection 
and  also  the  pressure-gauge  connection  as  often  as  needed  to  keep 
them  free  from  obstruction. 

Don't  neglect  to  clean  boilers  at  proper  times  to  suit  the  kind  of 
water  used,  by  first  drawing  the  fires,  and,  if  brick-set,  allowing 
sufficient  time  to  cool  the  walls  below  damaging  heat  by  opening  the 
doors  and  dampers;  then  blow  out  and  open  the  man-  and  hand-hole 
plates,  and  scrape  out  the  scale  arid  slush  with  a  long  hoe,  and  wash 
out  with  a  strong  stream  of  water  from  a  hose. 

Don't  forget  to  see  that  the  blow-off  pipe  is  clear  of  obstruction 
after  cleaning  boiler  by  drawing  water  through  it. 

Don't  neglect  to  clean  the  boiler-tubes  as  often  as  once  a  week, 
and  in  some  cases  twice  or  three  times  a  week,  according  to  the  draught 


THE  ENGINEER  AND  HIS   DUTIES  403 

of  the  chimney.  A  strong  draught  deposits  less  ashes  in  the  tubes 
than  a  weak  one. 

Don't  neglect  to  pump  up  your  boiler  to  the  upper  gauge-line 
when  stopping  the  engine  at  night.  Start  the  pump  before  closing 
the  throttle. 

Don't  forget  to  anticipate  the  stopping  of  the  engine  by  throwing 
open  the  fire-doors,  partly  closing  the  draught-doors,  and  opening 
the  dampers,  and  by  spreading  a  little  coal  over  the  fire  to  prevent  the 
sudden  rising  of  the  steam-pressure;  then  clean  and  bank  fires. 

Don't  hang  any  old  piece  of  iron  on  the  safety-valve  lever  to  stop 
sizzling.  It 's  a  dangerous  practice.  If  the  valve  leaks  regrind  it. 

Don't  neglect  to  search  for  and  find  the  cause  of  any  unusual 
occurrence,  noise,  or  knocking  in  the  engine  or  boiler-purnps,  nor 
put  off  the  remedy  to  some  more  convenient  time.  To-day's  doctor 
may  prevent  to-morrow's  disaster. 


QUESTIONS      AND      ANSWERS 

The  newly  fledged  engineer  applying  for  a  license  cannot  be  ex- 
pected to  answer  the  thousand  and  one  questions  that  may  be  contained 
in  the  catechisms  of  the  examiners  or  inspectors,  nor  to  understand  the 
whys  and  wherefores  of  the  elementary  strength  and  construction  of 
the  machinery  of  the  plant  that  he  is  to  take  charge  of.  It  is  sufficient 
if  he  has  at  hand  the  ready  wit  to  operate  and  care  for  it  and  to  know 
when  it  is  running  right  or  wrong,  and  what  to  do  when  confronted 
with  the  usual  troubles  of  a  power-plant.  The  progressive  engineer 
has  a  vast  field  before  him  in  which  to  explore  the  details  of  theoretical 
and  constructive  engineering  that  may  lead  him  to  the  head  of  his 
profession. 

We  append  a  limited  number  of  the  leading  questions  and  answers 
of  vital  interest  to  applicants;  but  in  publishing  them  do  not  wish 
to  depreciate  the  full  study  of  the  subject  as  shown  in  the  published 
catechisms  and  text-books. 

Question. — What  is  the  most  essential  part  of  a  steam-plant? 

Answer. — The  boiler,  whose  fire  and  water,  by  means  of  the  heat 
of  combustion,  generate  steam  under  pressure,  which  steam,  by  its 
expansive  force  in  an  engine,  creates  power. 


404  THE  ENGINEER  AND  HIS   DUTIES 

Question. — What  do  you  understand  by  combustion? 
Answer. — Combustion  is  the  production  of  heat  by  the  union  of 
the  oxygen  of  the  air  with  the  carbon  of  the  coal  in  the  fire. 

Question. — What  is  heat  as  you  understand  it? 

Answer. — Heat  is  a  property  of  matter  as  measured  by  its  tem- 
perature, and  the  quantity  of  heat  that  matter  can  hold  with  its 
change  of  temperature. 

Question. — Are  there  any  other  designations  in  regard  to  heat  or 
its  property? 

Answer. — Yes;  specific  heat,  which  is  the  capacity  of  any  body  in 
units  of  heat  to  raise  1  pound  of  it  1°  by  the  Fahrenheit  scale;  sensible 
heat,  which  is  the  measure  of  heat  as  indicated  by  the  thermometer; 
and  latent  heat,  which  is  the  unit  quantity  of  heat  required  to  vaporize 
liquids  or  fuse  solids  per  pound  of  their  weight. 

Question. — What  is  a  unit  of  heat? 

Answer. — A  unit  of  heat  is  the  standard  of  heat-measurement,  and 
is  equal  to  the  quantity  required  to  raise  1  pound  of  water  1°  by  the 
Fahrenheit  scale,  or  from  39  to  40°  F. 

Question. — What  are  the  essential  requirements  in  the  management 
of  the  fire  under  a  boiler? 

Answer. — A  clean  coal-bed  and  just  enough  air  to  produce  perfect 
combustion. 

Question. — What  do  you  consider  perfect  combustion? 
Answer. — The  hottest  condition  of  the  fire,  which  requires  2  pounds 
of  oxygen  for  the  perfect  combustion  of  1  pound  of  coal. 

Question. — How  much  air  is  required  per  pound  of  coal? 

Answer. — As  about  one-quarter  of  the  air  is  oxygen,  it  will  require 
10  pounds  of  air,  or  130  cubic  feet;  but  as  the  nitrogen  of  the  air  ob- 
structs combustion,  the  best  practice  requires  about  195  cubic  feet 
of  air  per  pound  of  coal  fed  to  the  furnace. 

Question. — What  is  the  effect  of  too  much  air  fed  to  the  fire? 

Answer. — It  has  a  cooling  effect;  as  only  the  exact  amount  of  its 
oxygen  can  be  taken  up  by  the  coal  to  form  carbonic-acid  gas,  any 
excess  of  air  dilutes  and  cools  the  gases  formed  by  combustion  before 
they  come  in  contact  with  the  heating-surface  of  the  boiler. 

Question. — What  is  the  effect  if  too  little  air  is  fed  to  the  fire? 

Answer. — The  combustion  is  imperfect,  and  carbonic-oxide  gas 
is  formed  of  one-third  of  the  heating-power,  due  to  the  coal,  which 
becomes  explosive  by  the  admixture  of  fresh  air. 


THE  ENGINEER  AND  HIS   DUTIES  405 

Question. — What  are  the  constituents  of  the  gases  from  a  boiler- 
furnace? 

Answer. — Principally  carbonic-acid  gas  (CC^),  carbonic  oxide 
(CO),  nitrogen  (N),  unconsumed  oxygen  and  its  nitrogen  (excess  of 
air),  and  steam  from  the  moisture  in  the  coal  and  air. 

Question. — What  effect  has  moisture  or  wet  coal  on  combustion? 

Answer. — They  absorb  heat  by  evaporation  inte^  steam,  and  retard 
the  heat  of  combustion. 

Question. — What  are  the  safety-appliances  usually  attached  to  a 
boiler  ? 

Answer. — Safety-valve,  three  gauge-cocks,  water-gauge,  pressure- 
gauge,  and  sometimes  a  draught-regulator,  fusible  plugs,  and  a  low- 
water  alarm. 

Question. — How  should  a  safety-valve  be  set? 

Answer. — To  blow  off  at  or  below  the  legal  pressure  allowed  for 
the  boiler.  If  a  much  lower  pressure  is  used,  5  pounds  above  the  usual 
requirement  will  be  sufficient. 

Question. — How  should  the  water-gauge  and  gauge-cocks  be  set? 

Answer. — So  that  the  middle  of  the  glass  and  the  middle  gauge- 
cock  should  be  on  a  level  with  the  proper  water-level  in  the  boiler — say 
from  4  to  6  inches  above  the  tubes,  according  to  the  size  of  the  boiler. 

Question. — Where  should  the  blow-off  be  attached  to  a  boiler? 

Answer. — At  the  back  end,  to  the  bottom  of  the  back  head,  or  to 
the  shell  for  best  effect;  sometimes  at  the  front  head,  with  or  without 
an  extension-pipe  reaching  to  the  back  of  the  boiler.  A  surface  or  scum 
blow-off  is  also  desirable  to  discharge  from  the  water-level. 

Question. — What  is  a  fusible  plug,  and  what  its  use? 

Answer. — A  screw-thimble  of  hard  brass,  filled  with  pure  Banca  tin, 
which  melts  at  442°  F.,  and  usually  screwed  into  the  crown-sheet 
of  locomotive-boilers  to  give  an  alarm  by  melting  and  blowing  out 
when  the  water-level  falls  below  the  crown-sheet. 

Question. — What  is  a  steam-drum,  and  what  its  use? 

Answer. — A  reservoir  from  which  usually  to  supply  dry  steam,  but 
of  doubtful  value  on  boilers  of  full  capacity  for  their  work,  as  the  drum 
weakens  the  shell. 

Question. — What  is  a  dry  pipe,  and  what  its  use? 

Answer. — A  perforated  pipe  along  the  upper  part  of  the  steam- 
chamber  of  a  boiler  for  distributing  the  area  of  the  steam-inlet  to  the 


406  THE  ENGINEER  AND  HIS  DUTIES 

steam-pipe,  and  thus  preventing  the  priming  or  entrained  water  from 
entering. 

Question. — What  is  an  automatic  damper,  and  what  its  use? 

Answer. — A  damper  that  is  operated  by  the  pressure  in  the  boiler 
acting  upon  a  regulator  that  opens  and  closes  the  damper,  and  thus 
controls  the  draught  to  equalize  the  boiler-pressure. 

Question. — What  is  the  effect  upon  the  water-line  of  suddenly 
opening  the  throttle  or  the  safety-valve? 

Answer. — With  small  steam-room  in  the  boiler  and  high  pressure, 
the  water  would  swell  up  by  the  liberation  of  steam,  show  a  rise  in  the 
water-gauge,  and  probably  carry  water  over  to  the  engine,  or  discharge 
water  from  the  safety-valve  in  case  it  was  lifted. 

Question. — What  are  the  first  requirements  of  an  engineer  or  fire- 
man when  he  enters  the  boiler-room  in  the  morning? 

Answer. — To  try  the  gauge-cocks  and  open  the  water-gauge 
valves  and  the  drip-valve  to  make  sure  of  the  water-level,  and  clear 
the  gauge-glass  connection.  See  that  all  valves  are  set  properly  as 
well  as  the  damper;  and  if  the  fire  has  been  banked,  haul  it  forward 
and  start  it.  Overhaul  the  pump  and  oil  it;  as  soon  as  there  is  steam 
enough,  start  the. pump  running  slowly;  and  do  likewise  with  the  in- 
jector, so  that  all  may  be  ready  at  the  time  for  starting  the  engine. 
See  that  all  oil-cups  have  oil,  and  that  all  parts  of  the  engine  are 
ready  to  start;  then  open  the  throttle  just  enough  to  clear  it  and  the 
pipes  from  water,  the  drip-cocks  also  being  open,  and  warm  up  the 
engine  under  its  slowest  possible  motion.  Give  it  time — if  a  small  one, 
one  or  two  minutes,  and  if  a  large  one,  three  to  five  minutes — to  grad- 
ually get  up  to  speed  after  the  engine  is  warmed  up  and  clear  of  water. 

Question. — What  is  the  effect  of  a  surplus  of  air  fed  to  a  boiler- 
furnace  ? 

Answer. — Air  in  excess  of  the  amount  necessary  for  perfect  com- 
bustion tends  to  cool  the  furnace  by  abstracting  heat  from  the  gases  of 
combustion. 

Question. — What  is  the  effect  of  feeding  wet  coal  to  the  furnace? 

Answer. — The  water  in  the  wet  coal  absorbs  heat  by  evaporation, 
which  does  not  produce  combustion  and  the  high  temperature  due  to 
combustion,  and  therefore  has  a  cooling  effect  upon  the  furnace. 

Question. — In  what  direction  is  the  steam-pressure  in  a  boiler 
exerted? 

Answer. — In  all  directions. 


THE  ENGINEER  AND  HIS   DUTIES  407 

Question. — What  part  of  a  boiler  has  the  greatest  pressure? 

Answer. — In  the  steam-space  the  pressure  is  equal  in  all  directions ; 
in  the  water-space  the  hydrostatic  pressure  of  the  water  must  be 
added  to  the  steam-pressure. 

Question. — -How  much  is  the  hydrostatic  pressure? 

Answer. — It  is  equal  to  T\3Q-  of  a  pound  per  square  inch  for  every 
foot  in  depth. 

Question. — If  the  upper  valve  on  a  water-gauge  were  closed,  what 
would  occur? 

Answer. — The  water  would  rise  to  the  top  of  the  gauge. 
Question. — Why  would  the  water  rise? 

Answer. — Because  the  steam  above  the  water  would  cool,  and  its 
condensation  would  draw  the  water  up. 

Question. — What  would  be  the  effect  of  closing  the  lower  valve  only  ? 
Answer.— The  gauge  would  gradually  fill  up  by  condensation. 

Question. — What  would  you  do  if  you  found  the  water  out  of  sight 
in  the  water-gauge? 

Answer. — Try  the  lower  gauge-cock,  then  open  the  drip-cock  to  the 
water-gauge.  If  no  water,  stop  the  engine,  throw  open  the  fire-doors, 
damp  the  fire  with  ashes  or  coal,  and  feel  the  check-valve  to  find  if  the 
pump  is  feeding.  If  not,  examine  the  pump,  and  if  it  has  occasioned 
the  trouble,  start  it  running  very  slowly,  when,  if  water  appears  in  the 
water-gauge  drip-cock,  increase  the  pump-speed  until  water  appears  in 
the  gauge-glass,  whereupon  regulate  the  fire  and  start  the  engine. 

Question. — What  would  you  do  if  the  boiler  commenced  to  foam 
excessively,  or  the  water-gauge  showed  excessive  motion? 

Answer. — In  ordinary  cases  increase  the  feed  and  blow-off  to  clear 
the  water;  if  not  found  sufficient,  check  the  fire,  stop  the  engine,  and 
prepare  to  clean  the  boiler. 

Question. — What  are  the  general  causes  for  the  foaming  of  boilers 
with  good  feed- water? 

Answer. — The  forcing  of  boilers  that  are  too  small  for  the  work 
assigned  them,  dirty  or  greasy  water,  and  boiler-cleaning  compounds. 

Question. — What  would  you  do  if  you  had  a  full  head  of  steam 
and  a  good  fire,  and  had  to  shut  down  suddenly? 

Answer. — Open  the  fire-doors  and  cover  the  fire  with  ashes  or  coal, 
start  or  increase  the  pump-speed,  and  if  the  steam  is  still  rising  in 
pressure,  lift  the  safety-valve. 


408  THE  ENGINEER  AND  HIS   DUTIES 

Question. — What  effect  has  the  steam  from  a  foaming  boiler  upon 
the  engine? 

Answer. — It  carries  water  to  the  engine,  which,  by  becoming  solid 
in  the  pipe  and  steam-chest,  is  liable  to  wreck  the  engine  by  its  solid 
filling  of  the  clearance  and  compression-space.  It  is  also  wasteful  of 
fuel. 

Question. — Suppose  that  the  pump  was  running  and  the  water 
was  going  down  in  the  boiler.  What  might  be  the  cause  and  where 
would  you  look  for  it? 

Answer. — Increase  the  speed  of  the  pump  and  feel  the  check- 
valve  to  find  if  it  is  working,  or  try  the  test-cock  on  the  force-pipe; 
find  if  the  water-supply  had  failed ;  if  there  was  no  action  of  the  pump, 
examine  the  pump- valves  for  faulty  action;  and,  if  necessary,  stop 
the  engine,  slacken  the  fire,  and  overhaul  the  pump  and  water-supply; 
also  examine  the  blow-off  for  leaks. 

Question. — How  would  you  find  if  the  pump  was  not  drawing 
water,  or  whether  there  was  a  stoppage  in  the  suction-pipe? 

Answer. — By  rapping  on  the  suction-pipe  to  find  whether,  by  the 
sound,  it  is  empty. 

Question. — If  you  were  feeding  with  an  injector  and  it  failed  to 
feed,  what  would  you  do? 

Answer. — Open  the  overflow  and  find  if  it  were  discharging.  If 
not  discharging,  examine  the  water-supply.  If  steam  were  not  dis- 
charging, open  the  injector  and  clean  out  the  passages.  Look  after 
the  boiler  condition  and  its  safety. 

Question. — How  often  would  you  clean  the  tubes  of  a  boiler? 

Answer. — That  would  depend  upon  the  kind  of  fuel  and  upon  the 
chimney-draught;  a  strong  draught  tends  to  clear  the  tubes.  With 
soft  coal  and  weak  draught,  every  other  day  with  a  steam-blower  or 
brush;  with  anthracite  coal,  once  a  week  is  sometimes  sufficient. 

Question. — How  often  should  a  boiler  be  cleaned  ? 

Answer. — That  depends  upon  the  kind  of  water  used.  With  hard 
water,  once  in  two  weeks,  with  a  daily  blow-off;  with  soft,  clear  river 
water,  once  a  month,  with  a  blow-off  every  other  day. 

Question. — What  is  the  difference  between  gauge-pressure  and 
absolute  pressure  ? 

Answer. — Gauge-pressure  is  zero  at  atmospheric  pressure,  while 
absolute  pressure  starts  from  a  perfect  vacuum — 14.7  pounds  per 
square  inch  less  than  the  mean  atmospheric  pressure. 


THE  ENGINEER  AND  HIS   DUTIES  409 

Question. — What  is  the  initial  cylinder-pressure? 

Answer. — It  may  ordinarily  be  the  gauge-pressure  in  the  cylinder 
at  the  beginning  of  the  stroke,  or,  for  the  purposes  of  computation,  the 
absolute  pressure  at  that  time. 

Question. — What  is  back  pressure? 

Answer. — It  is  the  retarding  pressure  on  the  piston  during  the 
stroke.  In  non-condensing  engines  it  is  that  of~^the  exhaust  above 
atmospheric  pressure,  while  in  condensing-engines  it  is  counted  from 
a  perfect  vacuum. 

Question. — What  is  the  mean  pressure  in  a  cylinder? 

Answer. — It  is  the  mean  forward  pressure  of  the  initial  and  expand- 
ing steam,  less  the  mean  back  pressure  from  the  exhaust  above  at- 
mospheric pressure,  or  in  absolute  pressure  above  a  vacuum. 

Question. — What  is  clearance? 

Answer. — It  is  the  difference  between  the  volume  of  the  piston- 
displacement  and  the  volume  of  the  cylinder-  and  steam-passages, 
and  varies  from  2  to  8  per  cent,  of  the  piston-displacement  in  vari- 
ous types  of  engines.  Its  economy  is  inversely  proportionate  to  its 
volume. 

Question. — How  can  the  loss  by  large  clearance  be  modified? 

Answer. — By  early  closing  of  the  exhaust  and  causing  compression 
to  near  the  initial  pressure. 

Question. — Is  the  elimination  of  clearance  possible? 

Answer. — No;  it  is  necessary  in  order  to  accommodate  the  lost 
motion  in  joints  and  prevent  the  piston  striking  the  heads. 

Question. — What  is  meant  by  working  steam  expansively? 

Answer. — It  is  the  cutting  off  the  steam-inlet  at  some  definite 
portion  of  the  piston-stroke  and  completing  the  stroke  by  its  expansive 
pressure. 

Question. — What  is  the  effect  of  using  steam  expansively? 

Answer. — Its  effect  is  in  the  economy  due  to  the  use  of  the  ex- 
panding properties  of  steam  below  boiler-pressure. 

Question. — To  what  extent  could  expansion  be  used  economically 
in  non-condensing  engines? 

Answer. — The  economical  nominal  expansion  can  be  carried  to 
about  one-twenty-fifth  of  the  absolute  steam-pressure. 


410  THE  ENGINEER  AND  HIS  DUTIES 

Question. — To  what  extent  for  condensing-engines? 

Answer. — About  one-fourteenth  of  the  absolute  steam-pressure. 

Question. — What  effect  has  the  clearance  on  the  actual  expansion? 

Answer. — The  clearance  lessens  the  nominal  expansion  ratio,  so 
that  the  actual  expansion  with  clearance  is  less  than  the  nominal 
expansion. 

Question. — How  early  may  a  slide-valve  cut  off? 
Answer. — About  five-eighths  of  the  stroke. 

Question. — How  can  an  earlier  cut-off  be  obtained? 

Answer. — By  the  addition  of  a  riding  cut-off  valve,  which  may 
be  adjusted  for  any  desired  cut-off. 

Question. — How  otherwise  may  a  short  cut-off  be  obtained? 

Answer. — In  a  four-valve  engine  with  one  or  two  eccentrics,  and 
in  the  Corliss  type  of  engine. 

Question. — How  is  the  speed  of  slide-valve  engines  controlled? 

Answer. — Generally  by  a  flyball-governor  operating  a  throttle- 
valve,  or  by  a  shaft-governor  that  varies  the  throw  of  the  eccentric 
and  of  the  valve. 

Question. — What  advantages  has  a  riding  cut-off  on  a  slide-valve? 

Answer. — It  allows  of  any  desired  variation  of  the  speed  and 
power  of  the  engine  by  a  great  range  of  the  cut-off,  and  the  full  value 
of  the  steam  used  between  its  greatest  range  of  pressure  and  tempera- 
ture. 

Question. — What  advantages  has  the  drop  cut-off  in  the  Corliss 
engine  over  the  riding  cut-off  in  other  engines? 

Answer. — It  makes  a  more  uniform  admission-pressure,  a  sharper 
head  to  the  expansion-curve,  and  a  better  control  of  the  terminal 
exhaust-  and  compression-pressures.  Its  peculiar  valve-gear  allows 
of  complete  control  of  the  movements  of  all  the  valves. 

Question. — What  is  a  condenser,  and  what  its  use? 

Answer. — Any  application  of  cold  water  for  reducing  steam  to 
its  primary  condition  of  water  and  its  use  in  the  steam-engine  is  to 
save  the  value  of  its  latent  heat  as  a  power-economy. 

Question. — What  are  the  principal  types  of  condensers  in  use? 

Answer. — The  jet-condenser,  in  which  a  spray  of  water  comes  in 
contact  with  the  exhaust-steam  in  a  chamber;  the  surface-condenser, 


THE  ENGINEER  AND  HIS   DUTIES  411 

in  which  the  exhaust-steam  is  condensed  on  the  surface  of  tubes 
made  cold  by  circulating  water;  the  siphon-condenser,  in  which  the 
exhaust-steam  is  drawn  into  and  condensed  by  a  single  jet  of  cold 
water  under  a  hydrostatic  vacuum  made  by  a  water-column  about 
34  feet  high. 

Question. — What  advantage  is  a  condenser  to  the  power-economy 
of  a  steam-engine? 

Answer.— It  will  add  from  12  to  a  possible  14  pounds  per  square 
inch  to  the  mean  effective  pressure  above  the  atmospheric  pressure. 

Question. — What  advantage  has  a  surface-condenser  over  the  jet- 
and  siphon-condensers  ? 

Answer. — It  allows  all  the  water  of  condensation  to  be  used  con- 
tinually, taking  the  place  of  impure  water.  It  is  of  especial  value  in 
the  marine  service  and  where  good  water  is  scarce. 

Question. — Why  are  high  steam-pressures  advantageous? 

Answer. — Because  of  the  greater  range  of  temperatures  that  can 
be  utilized  for  power  and  their  saving  in  steam  by  reduced  cut-off. 

Question. — What  are  the  objections  to  the  use  of  high  pressures? 

Answer. — They  increase  the  danger  of  rupture  at  weak  points  in 
boilers  and  pipes,  and  of  shock  of  moving  parts,  beside  decomposition 
of  lubricants,  increase  of  leakage,  and  larger  cost  of  the  power-plant 
to  meet  increased  pressure. 

Question. — How  is  the  economy  of  a  steam-engine  expressed? 

Answer. — In  the  pounds  of  steam  or  its  water  consumed  per  hour 
per  horse-power. 

Question. — Why  is  it  not  expressed  in  pounds  of  coal? 

Answer. — Because  the  boiler-duty  is  independent  of  the  engine- 
duty,  and  the  coal-duty  should  apply  to  both  boiler  "and  engine. 

Question. — What  is  superheated  steam? 

Answer. — Steam  is  superheated  at  any  temperature  above  that  of 
the  water  from  which  it  is  generated,  or  above  that  of  saturated  steam. 

Question. — What  advantages  are  attributed  to  superheat? 
Answer. — It  lessens  cylinder-condensation  and  its  waste  of  power, 
and  enables  perfect  expansion. 

Question. — In  what  types  of  steam-engines  is  it  most  useful? 

Answer. — In  compound  and  multiple-expansion  engines,  where  the 
loss  of  steam  by  condensation  is  greater  than  in  non-condensing  engines. 


412  THE  ENGINEER  AND  HIS  DUTIES 

Question. — What  may  be  the  possible  gain  by  superheating? 

Answer. — The  gain  by  superheat  depends  upon  the  method  of 
obtaining  it  and  its  amount — in  non-condensing  engines,  from  4  to  10 
per  cent. ;  in  condensing-engines,  from  6  to  14  per  cent. ;  and  in  multi- 
expansion  engines,  from  10  to  a  possible  20  per  cent. 

Question. — What  is  the  use  of  an  indicator? 

Answer. — To  show  the  general  conditions  of  the  work  of  the  steam 
by  means  of  the  form  of  the  diagram  that  the  recorder  makes  of 
pressures  and  volumes. 

Question. — Does  a  well-proportioned  diagram  show  an  economical 
engine  ? 

Answer. — Not  always;  leakages  may  balance  each  other  and  not 
affect  the  lines  of  the  diagram. 

Question. — What  does  an  ill-proportioned  diagram  show? 

Answer. — It  shows  where  to  look  for  the  faults  of  the  valve- 
motion  and  its  construction,  and  also  the  degree  of  steam-economy. 

Question. — What  other  important  properties  does  the  indicator- 
card  show? 

Answer. — A  faultless  diagram  shows  the  indicated  horse-power  of 
the  engine  and  the  quantity  of  steam  used  per  horse-power. 

Question. — What  is  the  use  of  a  governor? 

Answer. — To  regulate  the  speed  of  the  engine  automatically,  by 
varying  the  volume  of  steam  inversely  as  the  load. 

Question. — What  are  the  principles  of  action  of  governors? 

Answer. — The  throttling-governor  varies  the  initial  pressure,  and 
the  cut-off  governor  varies  the  volume  of  steam  by  varying  the  point 
of  cut-off. 

Question. — Which  is  the  more  efficient? 

Answer. — The  cut-off  governor  is  much  the  more  efficient. 

Question. — What  is  a  "stop  motion"  attachment  to  a  governor? 

Answer. — A  device  to  stop  the  steam-supply  in  case  the  governor- 
belt  breaks,  or  when  the  load  is  too  greatly  decreased,  which  over- 
speeds  the  engine. 

Question. — What  is  lead  on  a  steam-valve? 

Answer. — Lead  is  the  opening  slightly  of  the  steam-  or  exhaust- 
port  before  the  crank  reaches  the  centre. 


THE  ENGINEER  AND  HIS   DUTIES  413 

Question. — How  is  lead  obtained? 

Answer. — By  setting  the  eccentric  ahead  of  the  lap-angle;  it  is 
called  the  lead-angle  on  the  eccentric. 

Question. — What  is  lap  ? 

Answer. — It  is  the  extension  of  the  face  of  the  valve  over  the 
cylinder-ports  both  ways.  Laps  are  designated  as  steam-lap  and 
exhaust-lap. 

Question. — What  is  the  use  of  lap? 

Answer. — To  shorten  the  period  of  port-opening  from  greater 
valve-throw  and  its  quicker  motion. 

Question. — How  should  the  eccentric  be  set  for  the  proper  move- 
ment of  a  valve  with  lap  ? 

Answer. — By  advancing  the  eccentric,  so  that  the  steam-port 
just  opens  at  the  moment  that  the  crank  is  on  the  centre,  which  is 
the  lap-angle. 

Question. — What  effect  has  exhaust-lap? 

Answer. — It  increases  compression  by  retarding  exhaust-release 
and  possibly  choking  it. 

Question. — What  effect  has  increase  of  steam-lap  on  the  cut-off 
and  expansion? 

Answer. — It  shortens  the  cut-off  and  prolongs  expansion. 
Question. — How  early  may  a  plain  slide-valve  cut  off? 
Answer. — About  five-eighths  stroke. 

Question. — How  short  a  cut-off  may  be  obtained  with  a  riding 
cut-off? 

Answer. — From  zero  to  five-eighths  and  three-fourths  in  various 
makes  of  engines. 

Question. — What  is  the  range  of  cut-off  in  Corliss  engines? 
Answer. — From  zero  to  three-fourths. 

Question. — What  is  a  shifting  eccentric? 

Answer. — One  that  is  moved  from  its  centre  to  its  extreme  throw 
in  a  straight  line  by  the  varying  centrifugal  force  of  a  shaft-governor. 

Question. — What  is  a  swinging  eccentric? 

Answer. — An  eccentric  with  an  arm  pivoted  to  an  arm  of  the  fly- 
wheel, and  swung  in  a  circular  arc  from  its  centre  to  its  extreme  throw 
by  the  varying  centrifugal  force  of  a  fly-wheel  governor. 


414  THE  ENGINEER  AND  HIS   DUTIES 

Question. — What  are  the  advantages  of  high  piston-speed? 
Answer. — It  lessens   cylinder-condensation   and  enables  greater 
power  from  lighter  engines. 

Question. — What  are  the  disadvantages? 

Answer. — Greater  momentum  and  shock  from  the  moving  parts, 
causing  increased  wear  and  care  in  adjustment  and  lubrication. 

Question. — What  is  the  limit  to  fly-wheel  speed? 

Answer. — Practically  according  to  the  material  and  make-up  of 
the  wheel.  Cast-iron  wheels,  solid,  may  have  a  rim-speed  of  about 
6,000  feet  per  minute,  although  a  much  higher  has  been  in  use. 

For  the  progressive  young  engineer  there  are  a  thousand  or  more 
questions  which  by  their  answers  contribute  to  his  advancement 
and  success,  and  may  finally  put  him  at  the  head  of  his  profession. 

There  is  plenty  of  room  at  the  head,  and  it  only  requires  study  and 
practice  to  reach  it. 


ELECTRICAL    SECTION 


PREFACE 

THE  following  pages  have  been  prepared  for-  the  especial  use  of 
steam  engineers,  in  order  to  give  them,  at  a  glance,  the  essence  of 
modern  electrical  practice.  A  great  many  new  departments  of 
electrical  engineering  have  crystallized  in  the  last  ten  years,  and  in 
all  probability  more  will  assume  commercial  significance  in  the 
years  to  come. 

For  this  reason,  a  very  brief  theoretical  treatment  has  been 
given,  in  some  instances  sufficient,  it  is  believed,  to  indicate  the 
trend  of  future  progress.  The  author  knows  that  the  two  great 
problems  facing  the  engineer  in  charge  of  a  steam  plant  are :  First, 
to  keep  his  lights  burning;  and  second,  to  keep  his  power  supply 
going.  In  other  words,  the  steam  plant  and  the  electrical  plant  in 
conjunction  are  used  in  central  station  and  power-house  work  for 
lighting,  as  stated  above,  and  for  power  purposes. 

To  sum  the  matter  up  still  more  explicitly,  the  power-house 
and  centra]  station,  or  any  other  case  where  steam  and  electricity 
are  combined  for  a  common  purpose,  are  merely  an  instance  of 
where  electricity  of  a  certain  pressure  and  current  is  being  pro- 
duced. Its  production,  however,  necessitates  the  knowledge  and 
observance  of  certain  laws,  which  absolutely  govern  the  output  of 
current.  The  efficiency  of  the  plant  is  also  a  point  of  direct  im- 
portance, likewise  dependent  upon  the  care  and  management 
demonstrated  by  those  intrusted  with  such  a  responsibility. 

In  the  following  pages  of  text,  in  which  the  reader  will  find  a 
variety  of  subjects  treated,  of  direct  interest  to  the  engineer,  the 
author  believes  information  is  being  given  in  a  terse  and  useful 
form  for  immediate  use,  especially  in  conjunction  with  the  questions 
and  answers  appended. 

A  great  deal  of  ground  has  been  covered  in  these  pages,  and  a 
great  deal  of  information  necessarily  presented,  with  adequate 
explanations  under  the  circumstances.  The  point  kept  in  mind 
throughout  by  the  author,  however,  was  this :  that  the  engineer  is 

417 


418  PREFACE 

a  busy  man,  and  prefers  information  and  such  principles  as  are  by 
nature  part  of  the  facts,  given  in  a  simple  and  comprehensive 
manner.  Lengthy  explanations  composing  part  of  highly  complex 
analyses  would  hardly  be  the  thing  in  any  case.  Therefore, 
fundamental  principles  and  what  might  be  called  fundamental  facts 
compose  the  structure  of  the  text.  The  troubles  apt  to  arise  in  a 
piece  of  active  machinery  are  of  more  direct  importance  to  the 
steam  engineer  than  involved  theories.  Some  of  the  most  im- 
portant of  these  have  been  given  consideration  in  connection  with 
the  parts  of  a  dynamo  or  motor.  Lighting  in  its  various  forms 
has  also  been  reviewed  and  the  salient  and  practical  features  of 
each  given  distinct  attention. 

On  the  whole,  the  engineer  will  be  readily  able  to  test  the  value 
of  the  information  given,  by  utilizing  it  when  the  time  comes. 
It  is  the  author's  belief  that  it  will  prove  to  be  of  great  service,  not 
only  at  a  critical  time,  but  as  a  means  of  presenting  a  bird's-eye 
view  of  what  can  be  called  modern  electrical  practice. 

NEWTON  HARRISON. 

NOVEMBER,  1906. 


CHAPTER     XXIV 


THE    DYNAMO 
OPERATION     OF     THE     DYNAMO 

THE  operation  of  the  dynamo  may  be  best  and  most  briefly  described 
as  that  of  the  movement  of  conductors  with  respect  to  lines  of  force, 
or  of  lines  of  force  with  respect  to  conductors.  By  this  is  meant 
that  in  the  ordinary  type  of  direct-  or  alternating-current  generator 
this  idea  (Fig.  1)  predominates:  namely,  the  movement  or  cutting 
of  lines  of  magnetic  force  with  respect  to  conductors,  or  the  converse. 


N 


N 


\\ 


MOVEMENT  OF  CONDUCTOR 


I     \ 


MOVEMENT  OF  MAGNET 


FIG.  1. — Effect  of  moving  the  conductor  or  the  magnet. 

It  is  evident  from  this  statement  that  there  are  two  kinds  of  genera- 
tors :  the  direct  and  the  alternating  current.  It  is  readily  realized  that 
differences  must  exist  between  one  and  the  other  type,  distinguishing 
them  in  such  a  manner  that  they  stand  apart,  as  it  were,  representative 
of  two  systems.  These  differences,  which  are  the  means  by  which 
one  kind  of  current  is  known  from  the  other,  are  fundamental.  The 
direct  current  is  one  which  is  unvarying  or  unchangeable  (Fig.  2)  in 
its  direction.  The  alternating  current  is  one  which  is  constantly 
varying  or  changing  its  direction.  The  construction  of  generators,  and 
to  some  extent  their  operation,  are  based  upon  the  kind  of  current 
they  generate,  and  the  service  that  particular  current  performs. 

419 


420 


THE  DYNAMO 


The  operation  of  the  dynamo  in  general,  therefore,  represents  either 
the  movement  of  the  conductors  or  the  magnetic  field  relatively  in 


AN  ALTERNATING  CURRENT 


A  DIRECT  CURRENT 


ALWAYS  IN  ONE  DIRECTION 

EACH  WAVE  IN  AN  OPPOSITE  DIRECTION 

FIG.  2. — The  tremor  in  a  direct,  and  the  reversals  in  an  alternating  current. 

such  a  manner  that  by  means  of  a  commutator  (Fig.  3)  or  collector- 
rings,  or  by  dispensing  with  either,  electricity  is  produced  of  the  char- 
acter of  a  direct  or  alternating  current.  As  a  general  rule,  in  direct- 


.RMATURE 
WINDINGS 


FOUR  PART 
COMMUTATOR 


Use  of  commutator  converts  al-          Use  of  collector-rings  permits 
ternations  into  a  direct  the  natural  alternations 

current.  to  pass  outside. 

FIG.  3. 

current  generators  the  source  of  magnetism  or  the  field  remains  at 
rest.  The  armature  with  its  conductors  is  set  into  rotation.  In 
this  case  the  conductors  are  made  to  cut  the  lines  of  force  and  generate 
electromotive  force. 


GENERATING      ELECTROMOTIVE      FORCE 

A  dynamo  or  motor  is  simply  a  generator  of  electromotive  force. 
The  electromotive  force  produced  by  the  dynamo  is  utilized  for  lighting 
or  power  purposes.  The  electromotive  force  produced  by  a  motor 
serves  to  regulate  its  current-supply,  by  acting  automatically  and 
oppositely  to  the  pressure  sending  current  in.  The  electromotive 


THE   DYNAMO  421 

force  of  a  dynamo  is  calculated  and  developed  with  respect  to  the 
kind  of  work  it  is  to  perform.  For  instance,  it  will  be  115  volts  for 
incandescent  lighting,  or  500  volts  for  trolley-lines.  The  electro- 
motive force  is  generated  within  the  conductors  when  they  cut  the 
lines  of  force. 

The  basis  of  all  theoretical  and  practical  calculations  is  that  a 
volt  is  produced  if  lines  of  force  are  cut  by  a  conductor  at  the  rate  of 
100,000,000  a  second.  When  the  elements  of  revolutions  per  sec- 
ond, conductors,  and  lines  of  force  are  considered  together,  they 
may  be  conveniently  arranged  as  follows: 

Volts  =  lines  of  force  X  revolutions  per  second  X  conductors  on  the 
armature  -f- 100,000,000. 

Calling  the  volts  E,  the  lines  of  force  N,  the  revolutions  per  second 
S,  and  the  conductors  C,  the  formula  may  be  written: 

E  =  NxSxC^  100,000,000. 

For  instance,  if  it  is  desirable  to  generate.  115  volts,  the  field  N 
may  equal  5,000,000  lines  of  force  (Fig.  4),  the  conductors  C  may 


CONDUCTORS  =  100 


N 


Ft£LO.=-5,000,000  LINES  OF  FORCE 

FIG.  4. — Field,  speed,  and  conductors  producing  115  volts. 

equal  100,  and  the  s'peed  S  may  be  23  per  second.     On  this  basis  the 
formula  gives: 

115  volts  -  5,000,000  X 100  X  23  -*- 100,000,000. 

All  the  different  types  of  generators  are  constructed  on  this  prin- 
ciple as  a  foundation.  Whatever  variations  in  appearance  occur, 
they  cannot  be  regarded  as  other  than  differences  due  to  the  various 
applications  to  which  generators  are  put. 


422 


THE   DYNAMO 


USE     OF     THE     COMMUTATOR 

Beginning  with  the  generation  of  the  electromotive  force,  it  re- 
mains to  be  seen  how  the  direction  of  the  current  is  affected  by  it. 
It  may  be  stated  that  the  movement  of  a  conductor  past  a  magnetic 
north  and  south  pole  has  the  effect  of  not  only  generating  electro- 
motive force,  but  giving  it  direction,  so  to  speak.  By  this  is  meant 
that  a  copper  wire  moved  past  a  N  pole  will  have  a  current  pass 
through  it  in  an  opposite  direction  to  a  wire  similarly  moved  past 

a  S  pole.  Both  may  pro- 
duce exactly  the  same  elec- 
tromotive force,  but  the 
direction  of  the  current  the 
electromotive  force  sets  into 
action  will  be  opposite  in 
one  case  as  compared  with 
the  other. 

A  generator-field  consists 
of  two  or  more  magnetic 
poles  arranged  alternately. 
The  north  and  south  poles 
follow  each  other  respec- 
tively. Therefore  a  conduc- 

FIG.  5.— Currents  under  N  poles  flowing  out-     tor  wil1  produce  an  electro- 
ward.     Currents  under  S  poles  flowing  inward.       motive  f Orce  tending  to  Send 

a  current  in  opposite  direc- 
tions as  it  passes  a  N  pole  and  then  a  S  pole.  There  are  many 
conductors  on  the  armature  of  a  direct-current  generator.  Conduc- 
tors passing  S  poles  will  all  carry  a  current  in  the  same  direction. 
Conductors  passing  N  poles  will  all  carry  a  current  in  an  opposite 
direction  (Fig.  5)  to  those  passing  the  S  poles. 

The  problem  of  successfully  directing  these  two  opposite  but  si- 
multaneous flows  of  current  into  a  circuit  commonly  called  a  direct- 
current  circuit  is  solved  by  means  of  a  commutator  and  brushes.  The 
function  therefore  of  a  commutator  is  to  conduct  all  electricity  of  one 
direction  into  one  brush  or  set  of  brushes,  and  all  electricity  of  an 
opposite  direction  into  another  brush  or  set  of  brushes.  By  this 


THE   DYNAMO 


423 


means  the  naturally  alternating  current  generated  in  the  armature- 
conductors  of  a  direct-current  machine  is  rectified  or  commutated. 


REGULATING     THE      DYNAMO 

That  which  constitutes  the  regulation  of  a  dynamo  is  accomplished 
by  means  of  the  field  in  the  case  of  a  direct-current  incandescent- 
light  shunt-wound  machine.  The  field  is  either  increased  or  decreased 
in  strength,  this  being  the  means  by  which  the  electromotive  force 
of  the  armature  is  raised  or  lowered.  In  other  words,  the  fact  that 
the  armature  rotates  in  a  magnetic  field  of  more  or  less  lines  of  force 
is  an  evidence  of  the  generation  of  a  correspondingly  higher  or  lower 
electromotive  force.  For  instance,  if  115  volts  are  obtained  by 
means  of  5,000,000  lines  of  force  in  the  field,  acting  upon  100  armature- 


POINT  OF  RESISTANCE 

GIVING  A 
VOLTAGE  OF  138 


FIG.  6. — Effect  of  resistance  in  increasing  and  weakening  the  field  strength  and  the 

electromotive  force. 


conductors  rotating  at  a  speed  of  23  revolutions  a  second,  an  increase 
or  decrease  in  the  number  of  lines  of  force  would  mean  in  proportion 
just  the  same  change  in  the  volts  generated. 

If  the  5,000,000  lines  of  force  are  increased  to  6,000,000  or  lowered 
to  4,000,000,  the  volts  produced  (Fig.  6)  would  be  increased  to  138 
or  lowered  to  98.  In  other  words,  by  causing  a  variation  in  the 


424 


THE  DYNAMO 


strength  of  field  by  varying  the  current  in  the  field-coils,  a  degree  of 
effective  regulation  is  obtained  which  has  become  established  in 
common  practice  in  connection  with  what  are  called  shunt-wound 
dynamos. 


CLASSIFICATION      OF      DYNAMOS 

Dynamos  are  classified  under  two  general  headings:  first,  direct- 
current  generators;  secondly,  alternating-current  generators.  The 
direct-current  generators  are  further  subdivided  (Fig.  7)  into  series- 
wound  machines,  shunt-wound  machines,  and  compound-wound 
machines.  The  alternating-current  generators  are  classified  with 

SERIES  COILS 


LAMPS  IN  SERIES  LAMPS  IN  MULTIPLE  LAMPS  IN  MULTIPLE 

FIG.  7. — Three  types  of  direct-current  generators. 

respect  to  the  character  of  the  current  they  develop.  On  this  basis 
it  may  be  said  that  there  are  single-phase  machines,  two-phase 
machines,  and  three-phase  machines. 

Among  alternating-current  generators  are  found  forms  of  construc- 
tion of  a  special  character,  in  which  neither  the  armature- wire  nor 
field-wire  is  moved  when  electromotive  force  is  being  produced.  An 
essential  element  of  alternating-current  practice  is  the  transformer, 
by  means  of  which  the  voltage  is  raised  or  lowered  for  transmitting 
or  distributing  the  current. 


THE  DYNAMO  425 

REGULATION     WITH     A     SERIES-WOUND 
DYNAMO 

The  series- wound  dynamo  is  generally  employed  for  a  system  of 
electric  lighting  in  which  a  constant  current  is  necessary,  such  as 
high-tension  arc-lighting,  for  instance.  The  function  of  this  type  of 
generator  is  to  provide  a  current  of  10  or  12  amperes  and  a  voltage 
that  is  capable  of  being  adjusted  by  special  means  to  suit  the  number 
of  lamps  in  use.  The  arc-lamps  are  connected  in  series,  each  lamp 
taking  the  same  number  of  volts.  If  twenty  or  thirty  lamps  are  thus 
connected,  twenty  or  thirty  times  the  volts  required  for  one  lamp  is 
necessary.  Allowing  50  volts  as  the  amount  required  for  each  lamp, 
the  total  voltage  to  be  generated  would  equal  20x50  or  30x50,  or 
from  1,000  to  1,500  volts. 

Arc-lamps  as  now  used  may  be  of  the  open  or  closed  arc  type. 
By  this  is  meant  that  the  carbons  either  burn  in  the  open  air,  lasting 
only  about  eight  or  ten  hours,  or  are  enclosed  in  a  small  globe.  Each 
lamp  takes  50  volts  if  of  the  open  air  type.  If  of  the  closed  globe 
type  each  lamp  will  take  about  80  volts.  The  dynamo  must 
be  able  to  automatically  raise  or  lower  its  voltage  when  lamps  are 
turned  on  or  off.  When  more  lamps  are  added  to  the  line,  more  volts 
will  be  required;  in  fact,  as  much  more  as  there  are  extra  lamps. 

When  lamps  are  cut  out,  less  volts  will  be  required,  in  proportion  to 
the  number  of  lamps.  For  instance,  if  ten  lamps  of  the  closed  globe 
type  are  added  to  the  circuit  of  a  series-wound  dynamo,  by  simply 
turning  them  on,  10x80,  or  800  volts  more  must  be  sent  into  the 
line.  On  the  other  hand,  if  ten  lamps  are  cut  out,  800  volts  less  in 
the  line  will  do.  Fewer  lamps  turned  on  or  off  would  mean  the  same 
thing — more  or  less  volts  accordingly.  The  series- wound  dynamo, 
with  an  automatically  varying  voltage  as  described,  but  a  constant 
current,  meets  these  requirements  by  shifting  its  brushes  (Fig.  8) 
automatically  around  its  commutator.  This  is  based  upon  the  prin- 
ciple that  between  two  given  points  on  the  commutator  the  generator 
gives  out  its  highest  and  its  lowest  voltage.  If  the  brushes  can  be 
made,  by  means  of  the  attraction  of  an  electromagnet,  to  move  to 
such  points  of  the  commutator  that  these  points  will  supply  just  the 
volts  required  by  the  number  of  lamps  in  use,  the  problem  is  evidently 
solved. 


426  THE  DYNAMO 

The  actuating  magnet  which  causes  this  regulation  is  also  in 
series  with  the  line,  and  is  sensitive  to  the  current  in  the  line.  If  for 
an  instant  that  current  is  too  high,  the  power  of  the  magnet  is  sufficient- 
ly increased  to  move  the  brushes  over  to  a  point  where  the  pressure 
drops.  If  the  current  in  the  line  is  too  weak,  the  power  of  the  magnet 
reduces  sufficiently  to  permit  the  brushes  to  assume  a  new  position 


^-  COIL  WHICH  CHANGES  THE  POSITION  OF 

(        THE  BRUSHES  ON  THE  COMMUTATOR 
X 


LAMPS  IN  SERIES 

FIG.  8.— Method  of  shifting  the  brushes. 

on  the  commutator,  where  more  volts  may  be  sent  out  over  the  line. 
This  adjustment  is  continually  going  on  in  a  series  arc-light  machine 
of  modern  construction.  Though  other  methods  of  regulating  the 
voltage  and  keeping  the  current  constant  have  been  tried,  this  method 
has  been  generally  accepted  and  adopted  as  the  best  to  be  used  under 
the  circumstances  involved. 


REGULATION    WITH    A    SHUNT-WOUND    DYNAMO 

The  shunt-wound  dynamo  is  one  in  which  the  fields  take  but  a 
small  percentage  of  the  total  current.  In  large  generators  the  fields 
take  from  1  to  2  per  cent.,  or  even  less.  In  small  generators  the  field- 
current  will  represent  a  heavier  percentage  of  the  total  armature- 
current.  In  practice  a  resistance  is  inserted  in  the  field-circuit,  so 
that  its  manipulation  will  control  the  amount* of  current  passing  into 
the  field-winding.  When  a  shunt  dynamo  is  being  loaded  up,  the  ten- 


THE  DYNAMO  427 

dency  of  the  lamps  to  drop  in  candle-power  becomes  more  and  more 
apparent. 

The  causes  operating  to  bring  about  this  effect  are  found 
(Fig.  9)  in  the  machine  as  follows:  First,  drop  in  the  armature-con- 
ductors due  to  the  armature-current  passing  through  the  armature- 
resistance,  represented  by  CxR;  secondly,  demagnetizing-field  of  the 
armature,  through  which  the  influence  of  the  armature  as  an  electro- 
magnet opposing  the  field  proper  becomes  more  and  more  magnified. 
These  disturbing  influences  may  be  readily  understood  as  acting  as 
means  of  cutting  down  the  volts  obtainable  from  the  generator  to  a 
marked  degree,  unless  an  effective  remedy  is  employed. 

It  is  evident  that  the  volts  lost  in  the  armature,  through  drop  of 
potential,  can  only  be  compensated  for  by  generating  that  number 
of  volts  extra.  It  is  also  evident  that  the  reactive  magnetic  effect 
of  the  armature  can  only  be  compensated  for  by  providing  as  many 
more  lines  of  force,  or  as  much  more  magnetism,  as  has  been  ren- 
dered ineffective  by  it.  In  other  words,  the  only  way  to  regain  the 
volts  actually  lost  in  the  armature,  and  those  additional  volts  which 


REACTIVE  FIELD 

FROM  ARMATURE 


NORMAL  FIELD  REDUCED 
BY  THE  OPPOSING 
S    FIELD  OF  THE 

ARMATURE  COILS 


FIG.  9. — Armature-reaction  and  armature-drop  in  a  shunt-wound  dynamo. 

would  be  generated  in  it  were  some  of  the  power  of  the  field  not 
destroyed,  is  by  supplying  enough  extra  lines  of  force  when  required 
to  meet  this  emergency. 

For  this  reason,  therefore,  the  rheostat  inserted  in  the  field-circuit  is 
so  utilized  that  when  the  dynamo  is  running  with  a  light  load,  little 
or  no  current  passes  through  it.  When  the  load  is  increased,  the 
rheostat  is  so  adjusted  that  the  field- windings  take  more  current. 
Cognizance  of  the  candle-power  of  what  is  called  the  pilot-lamp,  or 
of  the  pressure  indicated  by  the  voltmeter,  will  enable  the  attendant 


428  THE  DYNAMO 

to  move  the  rheostat  to  the  proper  point.  This  is  not  an  automatic 
system  of  regulation,  because  of  the  constant  observation  required  of 
the  attendant.  Automatic  preservation  of  the  normal  or  working- 
lamp  pressure  is  obtained  by  means  of  the  compound-wound  gen- 
erator. 

REGULATION    WITH    A    C O M P O U N D - W O U N D     DYNAMO 

Preserving  the  pressure  automatically  by  means  of  a  compound 
winding,  simply  means  the  employment  of  a  winding,  or  rather  of 
two  windings,  one  of  which  is  simply  a  shunt  winding,  and  the  other  a 
series  winding.  In  other  words,  the  advantages  of  both  are  combined 
in  such  a  manner  that  when  the  generator  is  called  upon  for  more 
current,  it  provides  it  without  any  external  signs  of  a  drop  of  pressure. 


SHUNT  WINDING 


SERIES  WINDING  MAGNETIZES 

.IN  ADDITION.  AS  MUCH  AS  THE 

ARMATURE  CUTS  DOWN 


FIG.  10. — Series  winding  produces  lines  of  force  that  equal  those  the  armature 

destroys. 

Through  this  means,  at  a  low  point  of  load,  the  lamps  are  not  too  bright, 
or  at  a  high  point  of  load  too  dim.  The  general  principle  involved 
is  that  of  sending  through  a  few  turns  of  heavy  wire  (Fig.  10)  wound 
around  the  field  all  the  current  the  dynamo  generates.  In  this 
manner  the  more  current  the  dynamo  produces  the  stronger  it  makes 
its  field  in  consequence. 

When  there  is  little  or  no  current  coming  from  the  armature, 


THE  DYNAMO  429 

the  field  is  only  that  produced  by  the  shunt  winding.  Where  there 
is  a  heavy  current  produced  by  the  armature,  not  only  is  the  shunt 
winding  supplying  its  quota  of  magnetism  to  the  field,  but  its  effect 
is  augmented  to  the  extent  of  the  magnetism  supplied  by  the  few 
turns  carrying  the  total  current,  commonly  called  the  series-turns, 
in  contradistinction  to  the  shunt-turns.  Magnetism  is  therefore 
produced  in  the  compound-wound  machine  by  two  -sets  of  coils  whose 
effects  are  cooperative.  The  shunt  winding  in  such  a  case  does  not 
differ  in  character  or  principle  from  that  of  an  ordinary  shunt-machine. 
The  series  or  compensating  winding  is  there  for  the  purpose  of  adding 
as  much  additional  magnetism  to  the  field  as  is  required  to  compensate 
for  the  armature-reaction,  and  of  supplying  as  many  extra  volts  to 
be  generated  as  will  make  up  for  those  lost  by  drop. 

For  instance,  if  the  shunt-field  supplies  5,000,000  lines  of  force, 
and  the  armature  at  no  load  gives  115  volts,  the  machine  at  full 
load,  without  the  series-coil,  may  have  an  effective  field  of  only 
4,000,000  lines  of  force  and  give  only  95  volts.  This  would  mean  very 
bad  lighting  and  a  great  waste  of  power.  The  series-coil  therefore 
adds  enough  extra  magnetism  to  build  the  field  up  to,  and  keep  it 
constant  at,  a  little  over  5,000,000  lines  of  force.  A  little  over 
5,000,000  lines  of  force  are  necessary,  because  there  is  armature-drop 
as  well  as  field-reaction  to  compensate  for.  Thus,  in  a  case  where 
the  volts  drop  at  full  load,  from  the  initial  pressure  of  115  to  95,  the 
weakened  field  may  account  for  15  or  18  volts,  and  the  armature-drop 
for  about  2.  There  is  a  little  drop  as  well  in  the  series  winding  itself 
to  allow  for,  and  the  switchboard  and  the  heavy  mains  leading  there- 
to are  not  to  be  forgotten  in  including  all  possible  sources  of  loss  of 
pressure  in  the  machine  and  the  points  of  distribution  of  its  power. 


CHAPTER    XXV 

TESTING 
TESTING    A    DYNAMO    FOR    FAULTS 

A  DYNAMO  may  be  tested  for  faults  such  as  are  usually  denominated 
grounds,  short  circuits,  sparking,  or  failure  to  generate,  etc.  It  is 
best  to  treat  of  these  conditions  categorically,  in  order  that  each  may 
appear  in  its  true  aspect.  If  the  field-coils  are  grounded,  due  to 
moisture,  poor  insulation,  or  the  actual  contact  of  copper  to  iron, 
two  cases  are  presented:  first,  a  ground  in  one  coil;  secondly,  a  ground 
in  both  coils.  Heat  is  the  phenomenon  which  always  presents  itself 
in  one  or  more  coils  due  to  these  causes.  If  one  coil  becomes  heated 

to  a  much  greater  extent  than 
the  other,  the  cool  coil  is 
either  severely  grounded  or 
short-circuited. 

The  ground  may  have  oc- 
curred at  either  the  beginning 
or  the  end  of  the  coil.  If  at 
the  beginning,  the  coil  will  be 
cooler  than  if  it  had  occurred 
at  the  end.  By  this  is  meant 
(Fig.  11)  that  if  sufficient 
length  of  the  coil  carries  the 
current,  it  will  be  warmer 

than  if  it  only  passed  through  a  short  length  and  then  entered  the 
other  coil.  The  cooler  coil,  on  the  other  hand,  may  be  in  contact 
with  the  iron  or  itself  at  two  places.  In  such  a  case  it  will  be  short- 
circuited,  by  which  is  meant  that  a  greater  or  a  lesser  part  of  the 
winding  is  cut  out. 

If  a  greater  or  a  lesser  part  of  the  winding  of  one  coil  is  not  in 
circuit,  the  current  does  not  meet  with  the  same  resistance,  but  with 
less,  and  in  consequence  the  second  coil  is  carrying  too  much  current 

430 


THEMSELVES 


FIG.  11. — Wire  touching  iron,  and  wire 
touching  wire. 


TESTING  431 

as  well  as  part  of  the  first  coil.  For  two  coil-fields  this  is  true,  though 
the  same  principle  of  locating  the  cooler  coil  or  coils,  where  more 
than  two  coils  are  in  series,  will  enable  the  attendant  to  draw  conclu- 
sions as  to  the  ground  or  short  circuit  for  purposes  of  repair.  Baking 
a  coil  to  dispel  moisture  is  often  a  means  of  eradicating  latent  faults  of 
this  character. 

SPARKING 

Sparking  may  be  caused  by  too  great  a  load  on  the  dynamo,  or  by 
a  wrong  position  of  the  brushes.     One  brush  may  not  be  diametrically 
opposite  the  other  in  a  two-pole  machine,  or  the  brushes  may  not 
be  properly  adjusted  on  the  commutator  if  they  belong  to  a  multipolar 
machine.     If  a  four-pole  machine,  they 
should  be  90  degrees  apart,  if  a  six-pole 
machine,  60  degrees  apart,  etc.     The 
simplest  method  of  getting  the  correct 
distance  between  brushes  is  to  count 
the  commutator-bars  and  divide  them 
numerically  by  the  number  of  poles  of       FlG  i2._Mica  wearing  away 
the  generator.     Sometimes  the  cause  slower  than  the  bar. 

of  sparking  is  mechanical,  by  which 

is  meant  that  the  bars  may  be  loose,  or  either  the  bars  or  the  mica, 
or  both,  project  beyond  the  commutator  in  general.  The  difficulty 
is  frequently  found  (Fig.  12)  in  the  more  rapid  wearing  away  of  the 
copper  bars  before  the  mica  itself  has  worn  down. 

The  mica  is  a  mineral  product  of  a  greater  hardness  than  might 
have  been  expected,  and  in  consequence  the  friction  of  the  brushes 
affects  it  the  least.  Sandpapering  the  commutator  is  of  little  or  no 
use.  The  only  effective  remedy  is  that  of  turning  down  the  commu- 
tator— a  thing  best  done  by  a  lathe  or  by  a  special  commutator 
turning  device  found  on  the  market.  The  brushes  may  not  be  of  the 
proper  quality,  and  thus  cause  sparking.  For  instance,  as  a  matter 
of  information  it  may  be  stated  that  carbon  brushes  will  not  do  in 
all  cases.  Carbon  brushes  are  best  suited  to  hard-drawn  copper  bars, 
not  to  soft  ones.  Segments  of  a  less  durable  material  will  only  be 
ground  away  in  a  fine  powder,  whose  ultimate  injury  to  the  machine 
will  be  greater  the  longer  this  condition  exists.  In  addition  it  may  be 
stated  that  hard  or  soft  carbon  brushes  may  work  with  different 


432 


TESTING 


degrees  of  efficacy,  according  to  the  type  of  machine  and  the  nature 
of  the  design. 

There  is  such  a  thing  as  ineradicable  sparking,  due  to  bad  design. 
In  such  a  case  as  this  little  can  be  done  by  those  intrusted  with  the 
operation  of  the  machine.  Sparking  is  sometimes  caused  by  a  too 
small  air-gap  between  the  armature  and  the  field.  As  previously 
stated,  it  may  be  due  to  a  too  great  overload  of  the  machine.  There 
are  features  involved  in  the  design  of  a  sparkless  machine  which  bring 
into  close  relation  the  arc  of  embrace  of  the  pole-piece,  the  length  of 
the  air-gap,  the  ampere-stream  under  each  pole,  and  the  magnetic 
spray  from  the  pole-piece.  The  position  of  the  brushes,  which  gives 
what  is  called  sparkless  commutation,  is  largely  controlled  by  the 

existence  of  a  magnetic  fringe  which  extends 
beyond  the  leading  pole-tip. 

The  state  of  this  fringe  indicates,  in  certain 
respects,  a  measure  of  the  amount  of  spark- 
lessness  possible  to  achieve.  The  adjustment 
of  the  brushes  is  made  for  the  purpose  of 
securing  a  point  on  the  commutator  where 
the  reversal  of  current  in  the  successive 
armature-coils  passing  under  the  brush  or 
brushes  is  accomplished  without  sparking. 
This  magnetic  fringe  or  spray  is  effective  in 
reducing  inductive  effects  in  the  coil  or  coils 
undergoing  reversal,  by  introducing  an  op- 
posite influence.  Therefore  the  bad  effects  of 
reversal  when  the  brush  short-circuits  the 
coil  (Fig.  13)  and  the  influence  of  the  fringe 
counteract  each  other  if  the  design  of  the  machine  is  correct  in  these 
details.  Sparking  is  therefore  generally  inherent,  though  sometimes 
due  to  the  causes  noted  under  the  head  of  mechanical  defects,  or  to  a 
lack  of  judgment  in  selecting  a  suitable  brush  for  the  generator. 


SEGMENT 


POSITION  OF 
BRUSH  SHORT 
CIRCUITING 
A  COIL 


FIG.    13. — Time   at  which 
pole-piece  spray  is  useful. 


DYNAMO   FAILS  TO   GENERATE 

The  development  of  electromotive  force  is  the  primary  and  essen- 
tial feature  of  a  dynamo's  operation.  If  the  machine  will  not  "pick 
up,"  that  is  to  say,  begin  to  generate  its  electromotive  force,  there 


TESTING 


433 


are  certain  possibilities  causing  this  condition,  which  may  be  enumer- 
ated as  follows :  The  residual  magnetism  may  be  absent,  in  which  case 
it  must  be  restored  by  means  of  a  current  sent  into  the  field-coils 
in  the  right  direction.  The  magnetic  poles  of  the  machine  may  be 
the  same  (Fig.  14),  in  which 
case  the  connections  must  be 
changed.  The  field-coils  may 
have  an  open  circuit,  in  which 
case  they  must  be  tested,  and 
the  coil  or  coils  repaired. 

A  more  scientific  reason 
than  these  may  account  for 
the  inability  of  a  dynamo  to 
generate  electromotive  force 
by  referring  to  its  shunt-resist- 
ance and  speed.  In  other 
words,  the  simple  fact  of  the 
matter  is  this :  that  if  the  speed 
of  the  armature  is  not  suited 

to  the  resistance  of  the  shunt,  due  to  this  said  resistance  being  too 
great,  the  machine  will  not  generate.  There  is  what  is  called  a  criti- 
cal speed  for  shunt-  or  compound-wound  dynamos,  below  or  above 
which  normal  conditions  will  not  exist. 

If  the  generator  or  its  outgoing  circuits  have  made  a  double  ground, 
the  equivalent  of  a  short  circuit,  the  dynamo  will  not  generate.  A 
test  of  the  circuits  is  therefore  a  necessary  prelude  to  investigations 
of  this  character.  Faults  in  the  armature  itself  may  be  found  in  the 
nature  of  short  circuits  of  one  or  more  coils,  which  coils  will  get  very 
hot  on  running  the  machine,  this  condition  preventing  any  consider- 
able outside  pressure  from  appearing.  A  broken  coil,  on  the  other 
hand,  causes  sparking  and  the  blackening  of  the  bars  between  the 
ends  of  the  break. 


FIG.  14. — Case  in  which  the  poles  are  alike. 


CAUSE  OF  HEAT  IN  THE  ARMATURE 

The  existence  of  heat  in  the  armature  may  be  due  to  a  variety  of 
contributing  influences.  The  dynamo  may  be  overloaded,  or  the 
heat  may  issue  or  be  conducted  from  some  other  source  than  the 


434 


TESTING 


armature  itself.  There  may  be  difficulties  present  in  the  coils,  such  as, 
for  instance,  short  circuits.  The  armature  may  be  filled  with  dampness 
and  generally  grounded,  a  condition  removed  only  by  means  of  a  bak- 
ing process.  Certain  coils  may  be  so  wound  that  they  do  not  send  their 
currents  in  the  proper  direction.  If  the  winding  is  reversed,  a  form 
of  parasitical  current  of  large  amperage  develops,  causing  great  heat. 
A  source  of  disturbance  and  heat  is  discovered  in  the  use  of  very 
thick  copper  wires  or  bars.  The  effect  of  these  is  a  little  extraordinary 

in  the  sense  that  they  may 
develop  currents  within 
themselves  strictly  para- 
sitical in  nature.  The 
thick  bars  may  have  ed- 
dies of  electricity  (Fig.  15) 
flowing  in  them,  of  such 
strength  that  they  become 
intensely  hot.  These  ed- 
dies are  due  to  the  fact 

that  one-half  of  the  bar  longitudinally  is  developing  electromotive 
force,  while  the  other  half  is  not. 

They  may  occur  when  one-half  the  bar  is  affected  by  lines  of  force 
as  it  is  entering  under  a  pole-edge  a  little  sooner  than  the  other  half, 
simply  on  account  of  its  extreme  width  or  thickness.  The  brushes 
may  be  in  the  wrong  position,  on  the  other  hand,  and  give  rise  to 
heating,  or  two  commutator-bars  or  a  commutator-bar  and  the  frame 
or  bushing  may  touch  together.  In  running  a  generator  the  signs  of 
excessive  heating  must  be  carefully  watched  for;  otherwise  the  fact 
will  be  heralded  in  the  way  of  a  smell  of  burning  insulation  at  a  time 
when  the  need  of  light  and  power  is  of  vital  consequence. 


FIG.  15. — A  copper  bar  with  parasitical  currents. 


HEAT     IN     THE     COMMUTATOR     AND      BRUSHES 

Too  much  friction  (Fig.  16)  between  the  commutator  and  brushes 
is  a  prolific  cause  of  heat.  Yet  the  contrary  is  true,  that  when  the 
contact  between  them  is  insufficient,  heat  is  developed  due  to  the 
passage  of  the  current  through  a  comparatively  high  resistance. 
The  heat  generated  by  means  of  an  electric  current  is  measured  in 
watts  by  squaring  the  current  and  multiplying  by  the  resistance. 


TESTING  435 

For  instance,  if  10  amperes  are  passing  through  a  resistance  of  10  ohms, 
according  to  the  law  governing  such  cases,  the  watts  wasted  will 
equal  10  X 10,  the  current  squared,  multiplied  by  10,  the  ohms'  resist- 
ance, or  100x10-1,000  watts.  The  heating  effect  is  therefore 
measurable  by  the  waste  of  watts  on  this  basis.  And  the  heat  devel- 
oped may  be  also  noted  to  be  proportional  to  the  square  of  the  current 
in  amperes. 

By  this  is  meant  that  if  the  10  amperes  are  doubled,  the  watts 
will  be  quadrupled.  If  the  10  amperes  are  made  20,  the  watts 
wasted  become  20x20x10  =  4,000  watts  instead  of  1,000.  In  other 
words,  the  effect  of  twice  the  current,  from  the  heat  standpoint,  is  to 
multiply  the  heat  four  times.  The  effect  of  three  times  the  current 
would  be  to  multiply  the  heat  nine  times,  if  the  resistance  remains 
the  same. 

Where  commutator  and  brushes  are  concerned  or  any  conduct- 
ing part  carrying  a  very  large  current,  the  least  resistance  may 
mean  a  very  large  amount  of  wasted  power.  The  brush  may  press 

PRESSURE  OF  BRUSH  NORMAL  -PRESSURE  TOO  GREAT 


TEMPERATURE  120°  TEMPERATURE  200° 

FIG.  16. — Temperature  of  commutator  affected  by  brush  pressure 

properly,  but  may  have  too  great  a  resistance  and  develop  heat, 
or  the  casing  holding  it  may  not  make  the  proper  contact  and  cause 
heat  to  manifest  itself.  An  ordinarily  good  contact  will  prove  to  be 
very  deficient  in  any  case  where  a  very  heavy  current  passes  through 
it,  as  just  indicated. 

RADIATING  SURFACE  OF  COILS  AND  CURRENT- 
CARRYING  PARTS 

In  order  to  present  with  adequacy  the  subject  of  heat  in  the  various 
parts  of  an  electrical  machine,  it  is  necessary  to  touch  upon  the  physical 
or  geometrical  facts  (Fig.  17)  concerning  the  rise  of  temperature 


436 


TESTING 


SURFACE  TOO  SMALL 
TEMP.  =  150° 


WATTS 
WASTED  200 


in  conductors,  coils,  armatures,  commutators,  and  brushes.  As  far 
as  the  geometrical  facts  are  concerned,  it  may  be  said  that  the  larger 
the  surface  of  a  heated  body  the  more  rapidly  it  cools.  The  converse 

is  also  true,  that  the  smaller 
the  surface  of  a  heated  body 
the  hotter  it  becomes.  From 
the  standpoint  of  physics, 
however,  temperature  is  mere- 
ly an  indication,  so  to  speak, 
of  the  degree  of  concentration 
of  the  heat. 

By  this  is  meant  that  with 
a  given  quantity  of  heat,  say 
that  given  out  by  a  candle- 
flame  for  an  hour,  a  mass  of 
material  with  a  large  surface 


SURFACE  CORRECT 
TEMP.  =  100° 


WATTS 
WASTED  200 


FIG.  17. — Effect  of  radiating  surface  on  tem- 
perature with  the  same  waste  of  energy. 


would  not  show  a  high  tem- 
perature. A  small  mass  of  ma- 
terial, however,  would  show  a 
very  high  temperature,  particularly  if  its  surface  was  very  small. 
From  this  standpoint,  therefore,  temperature  is  dependent  upon  not 
only  the  amount  of  heat  actually  present,  but  the  rate  at  which  it 
is  being  radiated.  In  this  sense  a  conductor  carrying  electricity  and 
developing  heat  will  rise  in  temperature  according  to  the  amount  of 
metal  it  represents  in  proportion  to  its  outer  radiating  surface. 

Coils  carrying  electrical  energy,  such  as  field-  or  armature-wind- 
ings, or  commutators  or  brushes,  must  be  provided  with  sufficient 
surface  for  radiation  to  get  rid  of  the  heat  quickly  enough  to  pre- 
vent any  but  a  limited  rise  of  temperature.  In  steam-engineering 
the  general  problem  is  such  that  it  is  a  matter  of  economy  to  retain 
the  heat  as  far  as  possible.  In  electrical  engineering  the  process  is  gen- 
erally reversed.  Getting  rid  of  the  heat  as  quickly  as  possible  is  a  feat- 
ure of  daily  practice. 

TYPES      OF      MOTORS      IN      SERVICE 

The  types  of  motors  in  service  are  best  classified  under  the  titles 
of  series,  shunt,  and  compound  or  differentially  wound  machines. 
The  series  motor  is  one  in  which  the  speed  rises  to  a  destructive  point 


TESTING 


437 


without  a  load  or  curb.  The  shunt  motor  is  one  in  which  it  is  necessary 
to  have  a  resistance  in  series  with  the  armature  when  starting  it  up. 
The  compound  or  differentially  wound  motor  is  one  in  which  the 
series  winding  acts  either  to  increase  the  speed  of  the  motor,  or  to 
increase  its  pull  or  torque  with  a  heavy  load.  The  reason  why  the 
series  winding  acts  this  way  is  simply  because  with  one  method  of 
connecting  its  terminals  the  field  is  cut  down.  By  reversing  the  con- 
nections (Fig.  18)  the  field  is  built  up.  In  a  shunt  motor  the  weakening 
of  the  field  means  a  higher  speed.  The  strengthening  of  the  field 
means  a  greater  pull  and  a  lower  speed. 

Armature-coils  may  be  burned  out  or  grounded,  or  the  field  may 
be  deficient  in  the  motors  whose  types  are  given.  A  general  prin- 
ciple of  great  value  in  re- 
lation to  the  speed  and 
pull,  with  respect  to  the 
practical  application  of 
direct-current  motors,  is 
that  the  field-strength  and 
armature-current  are  the 
dominating  factors.  As  a 
general  rule,  the  greater 
the  armature-current  and 
the  strength  of  field,  the 
greater  the  pulling  power 
of  the  machine. 

There  is  such  a  condi- 
tion inviting  danger  to  the 
motor  as  too  low  a  speed. 
A  shunt-,  series-,  or  com- 
pound-wound motor  too 
heavily  loaded  will  natur- 
ally carry  too  much  cur- 
rent, heat  too  much,  run  too  slow,  and  probably  spark  too  much  in 
service.  A  shunt-  or  compound-wound  motor  running  too  fast  is  a 
case  (Fig.  19)  in  which  the  field  is  dangerously  weak.  The  shunt-coils 
in  such  a  case  should  be  carefully  examined,  and  the  series-coils 
reversed  in  connections. 

A  principle  enunciated  by  Jacobi  many  years  ago  relates  to  the 


FIG.  18. — Both  series  and  shunt  winding  acting  to 
increase  the  strength  of  the  field. 


438 


TESTING 


maximum  torque  of  the  armature  in  about  the  following  terms:  A 
motor  is  doing  its  maximum  work  when  it  is  loaded  to  such  a  point 
that  its  speed  has  become  one-half  the  normal  value.  In  other  words, 
the  heavy  loading  of  a  motor  may  be  effective  in  producing  a  surplus 
of  power,  but  this  is  only  done  at  the  sacrifice  of  efficiency.  The  over- 


FIG.  19. — A  shunt-  or  compound-wound  motor  with  no  field. 

loading  of  a  motor  therefore  to  the  point  noted,  namely,  half  the  speed, 
means  a  theoretical  efficiency  of  only  50  per  cent,  and  a  practical 
efficiency  of  even  less.  The  average  motor-efficiency  cannot  be  given 
in  exact  figures  except  for  a  given  size  and  type,  but  it  may  be  stated 
on  good  authority  that  it  is  over  80  per  cent,  and  less  than  95  per  cent. 
As  regards  the  armature-coils  being  burned  out  or  grounded,  or 
the  field-coils  exhibiting  deficiencies,  it  may  be  said  that  the  first 
case  will  be  manifest  in  the  shape  of  an  unusually  heavy  current 
with  probable  fuse-blowing  or  circuit-breaker  action;  the  second  will 
be  in  evidence  in  the  form  of  a  weak  magnetic  field  with  phenomena 
as  noted  in  the  way  of  high  speed  above  the  usual  value. 


SPARKING      IN     THE      MOTOR 

The  presence  of  a  very  high  speed,  and  a  line  of  sparks  around  the 
commutator,  with  two  of  the  bars  deteriorated  and  burned,  means 
a  case  of  open  circuit  in  the  armature-winding.  When  one  of  the 
coils  or  both  are  out  of  order,  so  that  little  or  no  field  is  present,  the 
armature  will  spark  badly  if  turned  by  hand  with  resistance  in  circuit. 


TESTING  439 

The  field-windings  may  be  opposed  to  each  other,  and  in  this  case 
the  armature  will  tear  itself  to  pieces  if  run  idle  without  a  preliminary 
examination  of  some  sort.  The  rules  which  seem  to  be  best  to  observe 
in  connection  with  shunt-  and  compound-wound  motors  is  to  see  that 
the  starting  resistance  is  in  series  with  the  armature  when  it  is  started, 
and  that  the  field  is  on  before  current  enters  the  armature. 


THE  BACK  ELECTROMOTIVE  FORCE  OF  A  MOTOR 

The  back  electromotive  force  of  a  motor  is  best  understood  as  due 
to  the  rotation  of  the  armature-conductors  in  the  magnetic  field. 
Through  this,  electromotive  force  is  generated  which  has  a  polarity 
opposed  to  that  of  the  entering  pressure.  To  distinguish  one  from 
the  other,  the  line-pressure  is  called  the  impressed  electromotive  force 
(Fig.  20),  and  the  armature-pressure  the  back  or  counter  electromotive 
force.  The  exact  value  of  the  back  electromotive  force  may  be  cal- 
culated by  means  of  the  current  and  the  armature-resistance. 

If  the  current  in  the  armature  at  any  point  of  load  is  multiplied 
by  its  resistance  and  the  product  subtracted  from  the  impressed 
electromotive  force,  the  difference  is  the  back  electromotive  force. 


DIRECTION 

THE  IMPRESSED 

OF  THE  BACK  E.M.F. 
E.  M.  F. 


FIG.  20. — Opposition  of  the  back  to  the  impressed  E.  M.  F.  in  a  motor. 

For  instance,  If  the  armature-resistance  is  .1  of  an  ohm,  and  the 
armature-current  50  amperes,  the  product  is  .1x50  =  5  volts;  sub- 
tracting this  from  an  impressed  electromotive  force  of  250  volts  would 
give  a  back  electromotive  force  of  250  —  5  =  245  volts. 

Electrical  efficiency  is  obtained  by  dividing  the  245  volts,  back 
electromotive  force,  by  the  250  volts,  impressed  electromotive  force, 
or  245-^-250  =  98  per  cent.  But  the  electrical  efficiency  is  not  the 
one  distinguished  by  the  title  "  commercial  efficiency."  This  last 
efficiency  is  equal  to  the  ratio  between  the  output  and  the  input;  or, 


440  TESTING 

in  other  words,  it  may  be  stated  that  the  commercial  efficiency  is  equal 
to  the  power  taken  out  divided  by  the  power  sent  in. 


HUMMING     AND      OTHER      NOISES     IN     MOTORS 

Humming  and  other  noises  are  associated  to  a  very  marked  extent 
with  motors  in  operation.  What  is  commonly  called  humming  is 
found  in  motors  in  which  the  armature-slots  carrying  the  conductors 

NES  OF  FORCE  SNAPP.NG        *™      n0t      P^peilj      TQ\&ted      tO 

the  pole-tips  of  the  machine. 
There  is  a  certain  snap  when 
the  armature-tooth  (Fig.  21) 
ARMATURE  leaves  the  pole-tip.   The  effect 

of  this  magnetic  snap  is  to  set 

up  a  molecular  vibration  in 
FIG.  21. — Cause  of  hum  between  pole- tip  ,         ,.  ,    . 

and  slotted  armature.  the   P°le>  Wmch  1S  Sometimes 

greatly  augmented  by  favor- 
able acoustic  conditions.  The  other  sounds  may  be  regarded  as  due  to 
a  vibration  of  the  brushes  with  respect  to  the  commutator  of  the  motor. 

A  peculiar  chattering,  as  it  is  called  in  the  machine-shop,  is  clue 
to  the  lack  of  proper  inclination  of  the  brush  or  brushes  to  the  com- 
mutator. The  commutator,  on  the  other  hand,  may  be  rough  and 
require  turning  down.  A  method  of  localizing  the  sound  is  to  lift  the 
brushes  off  the  machine  when  running  idle.  In  this  manner  it  is 
possible  to  ascertain  whether  the  noise  is  an  accentuated  hum  due  to 
the  armature-teeth  or  the  commutator  and  brushes.  A  little  oil  or 
vaseline  is  frequently  efficacious  in  this  respect.  It  is  good  practice 
to  file  the  brush  carefully  to  the  proper  angle  to  remedy  this  evil. 

Another  salient  cause  of  vibration  and  noise,  however,  is  the  lack 
of  balance  in  the  armature  itself.  It  is  a  common  practice,  after  a 
motor  or  dynamo-armature  has  been  completed,  to  test  it  for  mechan- 
ical balance  on  knife-edges.  It  is  sometimes  done  so  hastily  or  care- 
lessly that  the  balance  is  imperfect.  This  can  be  readily  discovered 
in  the  running  machine  by  means  of  the  hand  when  placed  upon  it. 
There  is  always  a  possibility,  however,  that  the  pulley  may  be  defec- 
tive. In  this  case  it  should  be  removed  and  carefully  turned  down 
until  balanced.  Removal  of  such  disturbances  better  insures  the 
period  of  usefulness  of  the  machine. 


CHAPTER  XXVI 

THE    SWITCHBOARD 

THAT  which  is  typified  by  the  name  of  switchboard  in  connection 
with  central  stations,  power-houses,  or  private  installations,  is  simply 
a  convenient  centre  from  which  or  to  which  all  important  conductors 
are  led  (Fig.  22),  and  at  which  the  instruments  and  protective 
apparatus  may  be  found.  The  switchboard  is  generally  made  of  slate 
or  marble,  and  of  sufficient  size  to  contain  on  its  polished  surface  not 
only  the  terminals  of  circuits,  but  a  variety  of  unique  but  never- 
theless indispensable  adjuncts  of  the  equipment.  It  is  necessary 
to  classify  the  elements  constituting  the  direct-current  switchboard 


MEASURING    INSTRUMENTS 


GROUND  DETECTOR       /^\  f\    TESTING 

ft  ft   ft    ft  ft 

CONTROLLING!  DEVICES 
PROTECTIVE  PROTECTIVE 


ft 


REGULATING 
RHEOSTAT 


j 


FIG.  22. — Circuits  connecting  to  switchboard. 

equipment  in  order  to  form  an  adequate  idea  of  its  importance  and 
serviceability.     This  classification  would  assume  the  following  form : 

1.  Measuring-instruments,  by  which  would  be  included  those  em- 
ployed for  the  measurement  of  volts,  amperes,  and  watts. 

2.  Controlling  devices,  by  which  would  be  included  all  switches 
controlling  main,  feeder,  and  subsidiary  circuits. 

3.  Protective  devices,  by  which  would  be  included  all  fuses,  cut- 

441 


442 


THE  SWITCHBOARD 


outs,  and  circuit-breakers  of  all  kinds  or  shapes  and  embracing  within 
that  scope  lightning-arresters  as  well. 

4.  Regulating  devices,  under  which  heading  the  rheostats  in  the 
fields  or  shunt-circuits  and  the  bus-bars  would  be  consistently  in- 
cluded for  this  purpose. 

5.  Testing  devices,  under  which  heading  would  be  included  ground- 
detectors  and  such  additional  instruments  as  may  be  used  to  serve 
the  same  purpose,  and  may  therefore  be  regarded  as  switchboard 
accessories. 

The  classification  of  the  wires  is  part  of  the  same  proposition, 
for  it  is  evident  that  the  original  purpose  of  the  switchboard  was  only 
to  coordinate  or  centralize  the  most  important  wires.  For  this  reason 
the  circuits  may  be  regarded  as  belonging  to  one  or  the  other  of  such 
divisions  as  the  entire  classification  of  the  switchboard  may  include. 


CLASSIFICATION     OF     CIRCUITS 

The  natural  arrangement  of  conductors  would  be  in  the  order  of 
their  essentiality  or  importance.  For  this  reason  the  wires  from  the 
dynamo  come  first  and  are  called  mains.  The  wires  from  the  mains 
are  generally  employed  as  supply-wires  or  feeders  (Fig.  23)  to  the  dis- 


GENERATOR 


FEEDERS 

FIG.  23. — Wires  named  in  their  order. 


tributing-wires  with  which  they  are  connected.  The  feeder-wires 
supply  current  to  the  branches,  and  by  means  of  the  more  important 
or  heavier  branch  wires  connect  a  class  of  sub-branches  or  subsidiary 


THE  SWITCHBOARD 


443 


circuits.  On  this  basis  there  appear  (1)  mains,  or  wires  from  the 
generator;  (2)  feeders,  or  wires  from  the  switchboard;  (3)  branches 
of  a  heavier  character  supplied  by  the  feeders;  and  (4)  sub-branches, 
or  final  distributing-wires. 


CENTRES     OF     DISTRIBUTION 

The  switchboard  carries  the  devices  which  exercise  the  various 
influences  noted  over  the  whole  system.  There  are,  however,  points 
on  each  floor,  or  group  of  floors  or  rooms,  in  which  a  secondary 
influence  may  be  exercised.  Such  points  are  called  "  centres  of  dis- 


BRANCH 

OR 

FEEDER 

s 

v 

/     U      U  LM  °     ° 

o  n  r^  o  o 

1 

O--o"o    O   ^ 

' 

.     /->      /~>  i       O     O 

i 

V 

y    O     0  1       u    u 
o    n  r^  o    o 

' 

0    0        10     0 

V 

U  ^°     ° 
o     o  1^^  n    o 

/ 

^ 

v 

y    O     O^°    ° 

ei  o  r^  o.  o 

? 

y 

O      O  1        O     O 

o  -    •-'• 

*s 

CIRCUIT  CONTROLLINoC 
SWITCHES 

( 

C 

)      ( 

O     OljO^O 

FUSES  — 

FIG.  24. — Use  of  a  panel  board  at  a  center  of  distribution. 

tribution."  They  appear  in  the  form  of  miniature  switchboards 
(Fig.  24)  which  are  devoid  of  other  than  controlling  and  protective 
appliances,  namely,  switches  and  fuses. 

The  feeders  enter  these  panel  boards,  as  they  are  called,  and  from 
them  various  branches  radiate  to  the  groups  of  lights  receiving  the 
current.  All  important  branches  connect  with  the  feeder  through  the 
medium  of  a  switch  and  fuse.  The  sub-branches  may  or  may  not 
be  provided  with  these,  depending  upon  the  character  of  the  lighting; 
but  the  entire  system  of  wires  on  this  basis,  from  the  generator  to 
the  lights,  is  adequately  protected  against  overflows  of  current. 


444 


THE  SWITCHBOARD 


SWITCHBOARD      APPLIANCES 

The  switchboard,  as  an  entity,  is  itself  subdivided,  according 
to  the  purpose  its  different  sections  serve.  These  sections  are  now 
made  in  distinct  panels  (Fig.  25)  or  part-switchboards,  according 
to  the  following  system : 

(1)  The  genera  ting-panel,  with  which  the  generator  connects  di- 
rectly with  its  controlling  and  protective  devices.  (2)  The  metering- 
or  load-panel,  with  which  the  voltmeter,  ammeter,  and  wattmeter 
connect.  (3)  The  feeder-panel,  with  which  the  outgoing  feeders, 
with  their  controlling-switches,  connect,  and  which  might  be  called 
the  distributing-panel.  (4)  The  testing-panel,  to  which  the  ground- 
detectors,  lightning-arresters,  etc.,  may  be  connected. 


AM.     VOLT.      AM. 


S.P. 

SWITCHES 


Dl.   VOLTMETER 


AMMETER 


CIR.    BR'K'RS 


GROUND    DETECTORS 

O — O 

o — o 

VOLTMETERS 


GR.D.   V.  M.   GR.D. 
SWITCHES 


GENERATOR  PANEL 


LOAD  PANEL 


FEEDER  PANEL 


TESTING    PANEL- 


FIG.  25. — Elements  of  a  switchboard. 


The  ammeter  or  ampere-meter  is  an  instrument  through  which  the 
entire  current  of  the  circuit  to  which  it  is  connected  passes.  By  in- 
dicating the  amperes  it  practically  records  the  number  of  lamps  in 
service,  unless  motors  are  also  feeding  from  the  line.  This  instrument 
is  always  placed  in  series  in  the  line,  not  in  multiple ;  if  placed  other- 
wise it  would  be  destroyed  or  greatly  disabled.  The  voltmeter  is 
always  placed  in  multiple  with  the  circuit  (Fig.  26)  whose  pressure 
it  indicates.  The  reason  for  the  difference  in  connections  of  the  am- 


THE  SWITCHBOARD 


445 


meter  and  voltmeter  is  found  in  the  great  difference  in  the  resistance 
they  represent. 

The  ammeter  has  the  least  possible  resistance;  the  voltmeter,  on 
the  contrary,  the  highest  possible  resistance.  The  ammeter  would 
cause  a  short  circuit  to  the  line  if  placed  across  its  terminals;  the 
voltmeter,  if  placed  in  series,  would  completely  block  the  passage  of 
the  current. 

The  wattmeter  indicates  the  product  of  the  two  elements  of  power 
noted  by  the  ammeter  and  voltmeter  (watts  =  amperes  X  volts),  and 


VOLTMETER    IN 
MULTIPLE 


AMMETER 
IN    SERIES 


FIG.  26. — Connections  of  a  voltmeter  and  ammeter. 

thus  gives  a  record  of  the  output  of  power  during  an  hour's,  day's, 
week's,  or  month's  operation.  It  is  an  excellent  record  of  the  output 
in  power  obtained  for  a  given  period  from  a  given  tonnage  of  coal. 

The  circuit-breaker  and  fuses  are  of  the  same  class,  though  of 
different  construction  and  operation.  They  both  serve  to  open  the 
circuit  (Fig.  27)  when  an  overflow  of  current  occurs.  The  fuse  melts 
or  volatilizes,  and  thus  destroys  the  continuity  of  the  circuit  it  con- 
nected. The  circuit-breaker,  through  the  medium  of  a  controlling 
electromagnet,  opens  a  switch  when  an  overflow  occurs. 

Both  devices  are,  in  this  sense,  comparable  to  the  safety-valve 
of  a  boiler ;  this  applies  particularly  in  the  case  of  the  circuit-breaker, 
whose  operation  is  electromechanical.  As  is  self-evident,  the  fuse 
must  be  replaced,  whenever  it  blows,  with  a  new  and  equivalent 
piece  of  fusible  metal.  The  circuit-breaker  is  simply  reset  by  means 


446 


THE  SWITCHBOARD 


of  a  catch  which  engages  with  the  armature  of  the  controlling  electro- 
magnet.    When  that  armature  moves  against  the  tension  or  pressure 


MMN  LINE  OPENED 


FIG.  27. — A  single  pole  circuit-breaker  with  action  of  magnet  and  spring  shown. 

of  a  set-spring — which  is  impossible  unless  the  current  rises  above 
a  certain  optional  value — the  catch  is  released,  and  the  carbon-armored 
jaws  of  its  switch  fly  open,  breaking  the  circuit  it  thus  protects. 

THE      LIGHTNING-ARRESTER 

This  device  is  simply  an  air-gap  interposed  between  the  line  and 
the  earth  (Fig.  28)  through  the  medium  of  two  pieces  of  metal  slightly 
separated  from  each  other.  The  idea  involved  is  that  static  dis- 


CYLINDERS 
^     OF 
METAL 


A  VERV  HIGH 
RE8ISTANCE,SUCH. 

AS  A  THINLY       >- 
CHARRED  SURFACE! 
OR  AN  OPEN  SPACE 


A  DOUBLE  POLE  NONARCINQ 
ARRESTER 


FIG.  28. — Two  types  of  arresters  in  use. 


THE  SWITCHBOARD  447 

charges  will  jump  the  air-gap  to  the  earth  instead  of  continuing 
along  the  conductors.  The  highly  oscillatory  nature  of  the  discharge 
leads  to  this  conclusion,  for  the  reason  that  a  rapidly  moving  quantity 
of  electricity  finds  a  greater  difficulty  in  permeating  a  conductor  the 
more  rapidly  it  oscillates. 

At  a  very  high  rate  of  oscillation — that  of  a  lightning-discharge 
in  fact — the  conductor  becomes  less  conductive  than  the  air.  The 
gap  in  the  arrester  thus  permits  the  charge  to  choose  and  pass  into 
the  earth.  A  wire  leading  up  from  an  earth-connection  to  a  piece 
of  metal — the  said  piece  of  metal  being  opposite  and  near  to  another 
connected  to  a  line  wire — represents  an  arrester  in  its  simplest  form. 
Variations  of  this  idea  predominate  in  practice  as  indicated  by  many 
manufactured  types. 

A    GR O UN D -D ET E CTOR 

As  its  name  implies,  this  is  a  device  by  means  of  which  a  ground 
between  the  mains,  feeders,  or  branches  and  the  earth  is  indicated. 
It  is  of  sufficiently  simple  construction  to  warrant  no  other  explanation 

4- 


FIG.  29.— Ground-detector. 


than  that  it  consists  of  two  lamps  in  series  (Fig.  29)  across  a  110-volt 
line.  The  junction  between  the  lamps  is  grounded  or  earthed.  When 
a  lamp  on  one  side  glows  brighter  than  that  on  the  other,  it  means  a 
ground  on  the  side  of  the  dim  lamp.  It  is  a  simple  and  effective 


448  THE  SWITCHBOARD 

method  of  determining  the  condition  of  the  circuit  before  the  power  is 
turned  on. 

The  existence  of  a  ground,  when  discovered  through  the  use  of 
this  device,  calls  for  immediate  investigation  and  a  systematic  search. 
In  order  to  facilitate  the  test,  the  feeder-switches  should  be  all  opened 
and  the  dynamo-mains  tested  first.  If  this  test  does  not  result  in 
discovering  the  ground,  each  feeder-circuit  should  be  thrown  in,  one 
after  the  other,  until  the  lamps  again  show  the  discrepancy  in  illu- 
mination noted  at  the  beginning. 

The  last  switch  to  be  closed  to  effect  this  result  is  the  one  govern- 
ing the  circuit  or  circuits  in  which  the  ground  exists.  The  investi- 
gation is  then  made  with  respect  to  the  heavier  and  then  with  the 
subsidiary  branches  of  this  particular  feeder-circuit,  until  the  fixture, 
chandelier,  motor,  or  other  source  of  trouble  is  discovered  and  the 
fault  remedied.  A  daily  test  to  protect  the  system  is  necessary  be- 
cause a  ground  on  both  legs,  if  heavy  enough,  would  constitute  a  short 
circuit. 

STORAGE-BATTERIES 

The  storage-cell  is  employed  for  a  distinct  purpose  in  central- 
station,  power-house,  and  private-plant  work.  Its  application  is  best 
found  in  central-station  and  power-house  service  as  a  means  of  averag- 
ing up  the  day-  and  night-load.  If  there  is  a  very  heavy  call  made 
for  current — a  demand  beyond  the  load-limit  of  the  generators — the 
storage-battery  serves  the  useful  purpose  of  adding  such  of  its  quota 
as  is  necessary  to  meet  the  demand. 

If  the  demand  is  frequent  but  spasmodic  there  is  no  substitute 
for  it  in  an  electrical  or  an  economic  sense.  In  other  respects  the 
storage-battery,  merely  as  a  convenient  electrochemical  device  for 
transforming  electrical  energy  into  chemical  energy,  is  an  interesting 
and  commercially  useful  invention.  Its  characteristics  may  be  readily 
comprehended  in  the  following  terms: 


TYPES      OF      S T O R A G E - B A T T E R I E S 

There  are  two  types  of  storage-cell,  the  Plante  and  the  Faure. 
The  Plante*  consists  of  lead  plates  that  have  undergone  the  process 
(Fig.  30)  called  "forming,"  whereby  the  lead-surface  for  a  considerable 


THE  SWITCHBOARD 


449 


depth  has  been  converted  into  an  oxide  of  lead.  The  positive 
plates — that  is  to  say,  the  plates  always  connected  with  the  positive 
pole  of  the  dynamo — turn  into  a  spongy  reddish  or  chocolate-colored 
mass.  The  negative  plates,  always  connected  to  the  negative  pole  of 
the  charging  current,  turn  gray  or  slaty  in  color,  due  to  the  develop- 
ment of  dioxide  of  lead. 

The  peroxide  of  lead  or  positive  plates  and  the  dioxide  of  lead 
or  negative  plates  are  thus  the  recipients  of  the  electricity  sent  in, 
storing  it  up  to  a  certain  point,  as  the  popular  expression  goes, 
called  "the  capacity  of  the  plates"  or  "cell."  The  solution  used  is 
that  of  a  20-per-cent.  sulphuric-acid  mixture,  or  four-fifths  water  and 


ELECTRICITY  ENTERING  AND 
PRODUCING  AN  ELECTRO-CHEMICAI 

CHANGE 


ELECTRICITY    LIGHTING 

A    LAMP    DUE   TO  THE 

ELECTRO-CHEMICAL  CHANGE 


FIG.  30. — Conversion  of  lead  into  active  material,  and  then  the  production 

of  electricity. 

one-fifth  acid.  The  acid  employed  for  this  purpose  is  comparatively 
pure;  otherwise  distressing  and  injurious  local  troubles  will  develop. 
The  Faure  cell  differs  from  the  Plante  in  the  respect  that  the  oxide  is 
not  formed  by  a  slow  electrical  process  of  charging  and  discharging 
during  a  period  of  many  weeks,  as  was  the  old  and  original  process, 
but  by  mechanically  applying  the  two  oxides  in  the  form  of  a  paste. 
The  pasted  grid  of  lead  or  some  lead  alloy  came  into  extensive  use 
(Fig.  31),  and  its  interstices  were  filled  with  a  paste  of  lead  oxide  and 
glycerine.  The  positive  grid  originally  received  a  red-lead  paste, 
which,  through  a  comparatively  brief  forming  process,  was  readily 
converted  into  peroxide  of  lead.  The  negative  plate  received  a  paste 


450 


THE  SWITCHBOARD 


of  litharge,  a  lower  oxide  of  lead,  a  comparatively  brief  forming  process 
converting  this  as  well  into  a  dioxide  of  lead. 

The  idea  in  connection  with  both  plates  was  to  get  a  spongy  mass, 
in  close  adherence  to  the  grid  supporting  it,  during  the  process  of 


DDDD 
ODDD 
D  D  D  D 
DDDD 


oooo 
oooo 
oooo 
oooo 


HOLE  FOR  PASTE 


PLUGS  OF  FINELY  DIVIDED  LEAD 


FIG.  31. — Appearance  of  grid  to  which  paste  or  a  process  is  applied  to 
rapidly  form  it  for  service. 

manufacture.  The  capacity  of  the  plates  individually  and  collectively 
was  thus  raised  to  a  certain  practical  working  maximum  by  which 
they  were  rated  when  sold.  This  rating  is  in  ampere-hours,  a  term 
meaning  the  number  of  amperes  normal  discharge  for  a  certain  num- 
ber of  hours.  For  instance,  100  ampere-hours  would  mean  about  10 
amperes  discharge  for  10  hours;  a  250-ampere-hour  capacity  would 
mean  about  25  or  30  amperes  respectively  for  10  or  8  hours.  The 
lower  the  rate  of  discharge  comparatively,  the  longer  the  number  of 
hours  of  service,  a  sudden  heavy  call  for  current  beyond  the  normal 
rate  being  likely  to  cause  serious  damage  to  the  plates. 

The  pasted  plate  and  the  pure-lead  plate  are  used  in  conjunction 
in  the  following  manner:  the  positive  plate  is  made  in  the  majority 
of  cases  of  finely  divided  lead,  upon  which  the  electrical  action  is  very 
rapid.  This  plate  is  used  in  connection  with  a  pasted  negative  plate. 
The  positive  wears  out  the  more  quickly,  and  is  therefore  replaced 
the  oftener.  It  must  therefore  be  made  as  strong  as  possible  be- 
cause of  the  peculiar  deterioration  to  which  it  is  subject.  The  nega- 
tive plate  may  outwear  the  positive  two  to  one  or  even  three  to 
one  in  some  instances. 


THE  SWITCHBOARD 


451 


DIFFICULTIES    WITH    PLATES 

The  difficulties  with  storage-battery  plates  are  at  least  twofold: 
First,  they  are  apt  to  sulphate  if  left  too  long  in  the  solution  without 
being  well  charged.  Second,  they  are  likely  to  bend  or  buckle  under 
the  influence  of  a  very  heavy  discharge.  The  sulphating  means  a  hard, 
flaky,  white  coating  of  sulphate  of  lead  (Fig.  32),  which  is  removed 
only  with  great  difficulty  by  scraping  or  by  heavy  charging  and  dis- 
charging. The  acid  in  this  case  simply  attacks  the  lead-surface 
when  the  plates  are  well  discharged,  and  starts  a  distinct  chemical 
action.  The  moral  of  this  is  never  to  permit  a  storage-battery  to  fall 
very  low  without  recharging. 

The  battery  is  generally  over  2  volts  when  normal,  and  when  well 
emptied  of  its  energy  about  1.9  volts  or  a  little  lower.     This,  however, 
is  the  limit  of  discharge 
per    cell    for    ordinary  _J 

forms   of   service.    The     • •*    ' — • 

buckling  or  bending  is 
caused  by  the  sudden 
strain  on  the  plates  by 
an  inordinate  discharge. 
The  rate  of  discharge 
which  is  considered  safe 
is  given  with  each  type 
of  cell  by  the  manufac- 
turer, and,  if  possible, 
should  not  be  exceeded. 
The  buckling  that  is  so 

apt  to  occur  in  the  plates  has  the  effect  of  loosening  the  plugs  of 
active  material,  which  may  drop  between  the  plates  and  cause  an  in- 
ternal short  circuit.  It  may  also  make  the  plates  touch  at  various 
points  unless  adequately  remedied.  The  means  employed  to  remedy 
this  difficulty  is  simply  that  of  making  plates  sufficiently  rigid  to  with- 
stand the  strain  without  injury.  In  other  words,  the  plates  of  modern 
batteries  are  made  thick  enough  to  remain  unaffected  throughout 
their  period  of  usefulness. 


PATCHES  OF  SULPHATE  OF 
LEAD  OF  WHITISH  COLOR 


FIG.  32. — Patches  of  sulphate  on  surface,  and 
bending  of  plate. 


452  THE  SWITCHBOARD 


EFFICIENCY      OF      STORAGE-CELLS 

A  comparative  test  of  the  efficiency  of  storage-cells  is  made  by 
simply  sending  into  each  a  given  amount  of  power  and  taking  it  out 
again  up  to  a  certain  point.  The  voltage  of  the  cells  will  give  a  fair 
idea  of  the  relative  value  of  each  cell  under  the  circumstances.  But 
this  is  not  conclusive,  as  it  is  necessary  to  take  into  consideration 
the  weight  of  each  cell  and  its  period  of  usefulness  in  making  a  fair 
estimate  of  its  respective  qualities. 

Cells  are  made  for  portable  and  for  stationary  use;  the  weight 
question  is  an  important  one  in  the  first  case,  though  unimportant  in 
the  second.  Portable  cells  always  deteriorate  much  quicker  than 
those  occupying  a  fixed  position.  Each  square  foot  of  active  plate- 
surface  will  give  certain  maximum  and  minimum  capacities  in  ampere- 
hours.  Each  set  of  plates  will  last  a  certain  period  of  time  under  the 
influence  of  a  certain  course  of  treatment.  The  commercial  problem 
is  that  of  increasing  their  period  of  usefulness;  the  scientific  problem 
is  that  of  increasing  their  capacity  for  a  given  size  and  weight  and  of 
eliminating  characteristic  defects. 


THE      BATTERY-ROOM 

A  battery-room  is  best  designed  with  reference  to  ventilation, 
drainage,  heating,  water-supply,  aisle-space,  floor-construction,  and 
absence,  as  far  as  possible,  of  metal-work.  The  charging  of  a  storage- 
battery  means  the  development  of  acid-spray,  whose  effects  are  highly 
deteriorative.  Not  only  must  the  room  be  constructed  so  as  to 
be  protected'  from  this  evil,  but  it  must  be  ventilated  effectively. 
Openings  near  the  ceiling  at  one  end,  and  near  the  floor  at  the  other 
end,  are  the  best  means  of  securing  a  clean  atmosphere.  The  sloping 
of  the  floor  must  be  sufficient  to  thoroughly  drain  it  when  wetted 
through  overflow,  accumulations,  or  during  the  process  of  flushing  it 
out. 

Too  much  cold  is  effective  in  reducing  the  capacity  of  the  cells;  for 
this  reason  the  battery-room  must  be  kept  at  a  moderate  temperature 
during  the  winter  season.  Inspection  is  necessary  at  all  times,  and 
in  order  to  accomplish  this  readily  the  cells  must  be  arranged  so  as  to 


THE  SWITCHBOARD  453 

be  easily  accessible.  Refilling  with  water  or  solution  must  not  be  a 
difficult  task  in  a  battery-room.  Having  the  cells  low  enough  down, 
with  an  aisle  on  each  side,  is  a  good  plan  if  space  permits. 

The  use  of  asphaltum  paint  is  a  good  protection  against  acid-spray 
wherever  it  may  deposit;  and  the  floor  of  the  room  should  be  made 
of  vitrified  brick  laid  on  concrete  and  filled  in  with  pitch.  To  have 
water  conveniently  at  hand  is  imperative  in  a  battery-room,  though 
the  use  of  distilled  water  is  far  more  preferable.  If  floor-space  is 
limited  the  cells  must  be  arranged  in  tiers,  each  of  which  must  afford 
enough  overspace  to  readily  handle,  inspect,  and,  if  necessary,  remove 
defective  cells  or  plates. 


CHAPTER    XXVII 

LIGHTING    AND    LAMPS 
ELECTRIC     LAMPS 

THE  sources  of  electric  illumination  have  developed  sufficiently 
to  represent  a  distinct  department  in  themselves,  and  are  of  equal  im- 
portance to  the  system  or  systems  of  electric  lighting  in  vogue,  with 
their  characteristic  accessories.  Electric  lamps  are  sufficiently  varied 
in  principle  and  construction  to  represent  a  classification  of  the 
greatest  interest,  and  they  may  be  divided  into  the  following  types : 

1.  Incandescent  lamps  that  employ  a  vacuum  to  protect  the  in- 
candescent mass  in  use  from  the  action  of  the  air. 

2.  Incandescent  lamps  that  do  not  employ  a  vacuum,  but  use  an 
incandescent  mass  which  is  inherently  inoxidizable. 

3.  Arc-lamps  which  employ  two  carbons  that  burn  in  the  air 
and  that  consume  in  about  eight  or  ten  hours. 

4.  Arc-lamps  which  employ  two  carbons  that  burn  in  the  air,  the 
carbons  having  a  metal  core,  which  develops  a  comparatively  long  arc 
of  unusual  light-giving  power. 

5.  Arc-lamps  which  employ  two  carbons  that  burn  in  a  closed 
globe,  through  which  they  last  100  or  more  hours. 

6.  Incandescent-vapor  lamps  that  use  an  incandescent  mercury 
vapor  to  produce  illumination. 

7.  Incandescent-tube  lighting  that  is  effected  in  long  tubes  devoid 
of  air,  but  filled  with  a  highly  illuminative  gas  when  affected  by  a  cur- 
rent of  the  proper  pressure  and  character. 

The  incandescent  lamp  with  a  carbon  filament  and  the  closed  globe 
or  enclosed  arc-lamp  are  the  two  most  prominent  types  of  lamps 
(Fig.  33)  in  use  to-day.  The  arc-lamp  which  burns  with  exposed 
carbons  has  been  modified  by  the  introduction  of  a  metal  core  and  a 
specially  impregnated  carbon,  and  thereby  given  a  new  lease  of  life. 
It  bears  the  general  title  of  the  flaming  arc  for  reasons  that  will  be 
obvious  when  it  is  realized  that  metallic  vapor  is  effective  in  this 

454 


LIGHTING  AND   LAMPS 


455 


BURN  IN  AIR 


METAL 
CORE 


i  i 

tr 


ARC      '[(         LONG 


ARC  STARTED 
BY  TILTING  TUBE 


FIG.  33. — Types  of  electric-light  sources  in  present  use. 

respect  to  a  marked  degree,  by  enabling  an  ordinary  arc  to  be  elon- 
gated sufficiently  to  give  light  not  only  from  the  carbon  terminals, 
but  from  the  arc  itself. 


THE     INCANDESCENT     LAMP 

The  carbon  filament  of  an  incandescent  lamp  is  obtained  by 
carbonizing  a  fine  string  of  cellulose,  enclosing  it  in  a  glass  globe  from 
which  the  air  has  been  removed,  providing  it  with  platinum  leading- 
in-wires,  so  that  both  the  metal  and  the  glass  will  expand  and  contract 
together  and  thus  preserve  the  vacuum,  and  attaching  it  to  a  suitable 
base  for  commercial  purposes.  A  lamp  of  this  character  is  generally 
used  on  a  115-volt  circuit,  and  takes  a  current  of  from  .4  to  .5  of  an 
ampere.  The  value  of  the  lamp  commercially  is  naturally  based  upon 
three  considerations:  (1)  The  cost  in  barrel  lots;  (2)  the  life  in  hours 
of  normal  candle-power,  and  (3)  the  amount  of  candle-power  per  unit 
of  power;  as,  for  instance,  the  number  of  watts  per  candle  or  per  lamp 
of  16  candle-power. 


456  LIGHTING  AND  LAMPS 

The  cost,  durability,  and  efficiency  have  been  the  governing  influ- 
ences hi  developing  incandescent-lamp  manufacture  to  its  present 
point  of  perfection.  In  the  central  station  or  private-plant  the  effi- 
ciency and  durability  of  lamps  are  points  of  vital  importance.  The 
question  in  this  case  is  fundamentally  that  of  the  cost  of  the  candle- 
power  hours.  Incandescent  lamps  vary  in  this  respect,  one  producing 
more  candle-power  hours  at  a  given  power  or  watt-consumption  than 
another.  The  lamp  lasts  from  500  to  600  hours  under  ordinary  con- 
ditions, the  unit  of  power  adopted  being  that  of  16  candle-power. 


UGHT16C.P.NEW  UOHT12C.P  L.OHT10C.P 

OURS  varies  in  efficiency  as 
the  life  of  the  lamp 
increases.  It  grows 
less  illuminative  with 
a  given  amount  of 
power,  and  therefore 
becomes  less  efficient. 
FIG.  34.—  Relative  light  of  old  and  new  lamps.  In  fact,  the  net  COn- 

clusion    inevitably 

reached  is  that  old  lamps  are  very  wasteful  (Fig.  34),  as  may  be  readily 
shown  as  regards  the  light  they  give  and  the  watts  they  consume.  For 
instance,  a  new  16  candle-power  lamp  will  use  .4  of  an  ampere  and 
115  volts,  or  .4x115=46.0  watts.  At  the  end  of  600  hours  it  will 
require  55  or  60  watts  to  give  the  same  light. 

The  fact  that  the  old  lamps  do  not  break  is  a  temptation  to  use 
them;  but  the  difference  between  60  and  46  watts  is  14,  or  nearly 
33J  per  cent,  more  power.  If  the  pressure  is  not  raised  the  old  lamps 
will  give  no  more  than  10  or  12  candle-power,  thus  causing  a  waste 
either  way  of  practically  33J  per  cent,  of  the  fuel.  Old  lamps  or 
inefficient  lamps  are  simply  coal-wasters,  which  cost  more  in  fuel  than 
it  would  cost  to  buy  new  lamps. 

As  the  primary  purpose  of  a  plant  is  to  supply  a  certain  amount  of 
light,  it  seems  self-evident  that  the  keeping  of  it  up  to  a  normal 
value  is  a  responsibility  that  cannot  be  carried  out  without  adequate 
means.  For  this  reason  the  efficient  lamp  is  a  saving,  because  it 
means  not  only  less  coal,  but  less  wear  and  tear  of  machinery,  less  rate 
of  depreciation,  in  fact,  in  providing  satisfactory  lighting.  With  re- 
spect to  the  arc-lamp,  10  amperes  and  115  volts  in  incandescents 


LIGHTING  AND  LAMPS 


457 


will  light  about  20  or  25  lamps  of  16  candle-power,  or  produce  about 
300  or  400  candle-power.  An  arc-lamp  of  the  enclosed  type,  taking 
the  same  watts,  will  produce  from  1,200  to  2,400  candle-power,  the 
ratio  of  light  produced  being  as  4  or  6  is  to  1  in  favor  of  the  arc 
as  far  as  efficiency  is  concerned. 


THE      NERNST      LAMP 

This  lamp,  in  which  a  piece  of  rare  oxide  burns  in  the  open  air, 
is  more  efficient  than  the  incandescent  lamp  so  called,  because  the 
temperature  of  the  incandescent  mass  is  raised  so  much  higher.  In 
other  words,  the  whole  question  of  efficiency  in  incandescent  lamps 
hinges  upon  that  of  temperature.  If  a  carbon  filament  could  stand 
the  temperature  at  which  the  rare  oxide  burns  (Fig.  35),  the  efficiency 
would  double.  Instead  of  taking  from  3  to  4  watts  per  candle-power, 
it  would  take  from  1.5  to  2  watts.  But  carbon  will  not  stand  this 
heat  under  ordinary  circumstances  for  any  length  of  time. 


GLOWER 
1        4 


TEMPERATURE 
IS  HIGHER  THAN 
CARBON  FILAMENT 


1 .5  WATTS  PER  C.  P. 


LOWER  TEMPERATURE 
THAN  GLOWER 


ABOUT  3   WATTS  PER  C.P.  NEW 


FIG.  35. — Power  consumed  for  light  at  higher  temperatures. 

The  lamp  mentioned  above,  however,  using  the  rare  oxide  in  air, 
requires  that  this  oxide  be  primarily  heated  before  sufficient  current 
will  pass  to  heat  it  individually.  An  automatic  heater  is  therefore 
used  for  this  purpose.  The  filaments  of  these  lamps  are  technically 
called  "glowers,"  of  which  one,  two,  or  more  may  be  used  in  a  given 
case.  The  light  is  produced  at  the  rate  of  about  1.5  watts  per  candle- 
power,  or  at  twice  the  average  efficiency  of  new  incandescent  lamps. 


458 


LIGHTING  AND  LAMPS 


THE     OPEN     ARC 

By  the  term  "open  arc"  is  meant  the  type  of  lamp  in  which  the 
carbons  burn  in  the  open  air.  In  this  type  the  carbon  tips  and  the  arc 
combine  to  produce  light.  The  tips  are  in  some  instances  the  most 
effective,  particularly  in  the  enclosed  type.  The  arc  gives  an  average 
rated  spherical  candle-power  of  about  2,000  with  a  current  of  10 
or  12  amperes  and  about  50  volts.  This  means  two  lamps  in  series  on 
a  115-volt  circuit.  For  high-tension  lighting  the  lamps  are  arranged 
in  series,  2,000  volts  being  sufficient  to  light  forty  lamps  in  series. 
The  difficulty  and  expense  are  found  in  the  removal  of  the  carbons, 
their  cost,  and  the  general  attention  required. 


THE      FLAMING-ARC      LAMP 

The  accentuation  of  the  light  and  length  of  the  arc  itself,  as  pre- 
viously stated,  is  a  source  of  light  which,  bearing  the  descriptive  name 
of  the  "flaming  arc,"  has  proved  exceedingly  efficient  as  an  outdoor 


METAL  CORED 
CARBON 


UGHT  OBTAINED  FROM 
CARBON  ENDS  AND  ARC 


LIGHT  OBTAINED 
MAINLY  FROM  THE  ARC 


FIG.  36. — Principle  of  the  ordinary  and  the  flaming  arc  lamp. 

illuminant.  The  production  of  gases  limits  its  use  for  indoor  illumina- 
tion, except  in  such  cases  where  the  ventilation  is  excellent,  thereby 
rendering  the  gases  unde  tec  table.  The  lamps  burn  two  in  series,  on  a 


LIGHTING  AND   LAMPS 


459 


115-volt  circuit,  the  carbon  tips  (Fig.  36)  as  well  as  the  flame  of  the 
arc,  with  its  metallic  constituents,  developing  an  enormous  illumination 
— at  least  three  or  four  times  greater  than  that  of  the  ordinary  arc  as 
far  as  effective  light  is  concerned. 

The  carbons  are  replaced  about  every  day,  and  the  lamp  inspected 
and  readjusted  no  oftener  than  the  ordinary  open-arc  lamp.  A  resis- 
tance in  series  is  employed,  placed  in  the  upper  part  of  the  lamp,  to 
limit  the  current  when  supplied  with  a  higher  voltage  than  necessary. 
The  carbons  in  this  particular  type  are  held  at  an  angle  with  the 
vertical  plane,  thus  equably  reflecting  the  light  from  the  flaming  arc 
as  well  as  permitting  it  to  be  well  distributed  spherically.  By  means 
of  the  carbons  the  light  developed  is  of  a  golden  or  a  reddish  tinge. 
The  candle-power  is  about  4,000  per  lamp  or  over,  and  is  remarkably 
effective  on  account  of  its  peculiar  quality  due  to  the  salts  used  to 
impregnate  the  carbons. 

THE      ENCLOSED      ARC 

This  is  an  open  arc  with  the  carbon-ends  adjusted  to  a  globe 
supplied  with  an  outlet-valve.     The  oxygen  is  quickly  burnt  up, 
and  the  burnt  air  (Fig.  37)  in  conse- 
quence has  little  or  no  effect  upon  the 
carbons,  which  thus  last   100  or  150 
hours  instead  of  10  or  15. 

A  saving  in  carbon  and  care  is  thus 
in  evidence,  which  is  counter-balanced, 
however,  by  the  deposits  on  the  globe 
and  the  cutting  down  of  the  light. 
These  lamps  take  about  100  volts,  in- 
stead of  50,  on  account  of  the  length  of 
the  arc,  and  are  therefore  heavy  users  of 
current  and  pressure  on  115-volt  cir- 
cuits. The  economic  question  is  that  of 
evaluating  the  cost  of  carbons  and  labor 
against  the  cost  of  extra  power.  Into 
this  estimate  the  consideration  of  safety 
must  enter  on  account  of  the  closed 
character  of  the  lamp  and  the  resultant 
candle-power. 


THE  ARC  BURNS] 

UP  THE  OXYGEN  >•» 

LEAVING  C02  J 


FIG.  37. — The  carbons  burn  with 
flat  ends. 


460 


LIGHTING   AND   LAMPS 


M E RC U R Y- V A P O R     LAMP 

In  this  lamp  a  tube  with  electrodes  forms  an  arc  of  mercury,  in 
which  band  of  dazzling  light,  however,  all  red  rays  are  missing.  This 
defect  exhibits  itself  in  the  development  of  ghastly  flesh-effects,  green 
and  blue  (Fig.  38)  causing  a  livid  appearance  of  the  lips,  face,  and 
hands.  For  this  reason  this  lamp  cannot  be  used  for  domestic  or 
ornamental  lighting,  but  is  serviceable  for  docks,  factories,  ware- 


FIG.  38. — Experiment  with  red  glass — which  can  only  transmit  red  rays — to  prove 

the  absence  of  red  light.  , 

houses,  etc.  The  tube  is  automatically  tilted  to  start  the  arc  by  per- 
mitting a  thin  stream  of  mercury  to  volatilize  between  the  electrodes. 
The  efficiency  of  this  lamp  is  high  enough  to  establish  its  commercial 
value  on  a  permanent  basis. 


VACUUM-TUBE      LIGHTING 

The  use  of  a  150-foot  tube,  through  which  an  alternating  current 
passes,  is  a  development  of  Geissler's  early  experiments  on  a  commer- 
cial scale.  The  so-called  vacuum,  in  conjunction  with  certain  gases, 
is  a  source  of  illumination  which  has  found  a  place  in  daily  practice. 
The  absence  of  wires  in  all  but  one  spot  where  the  tube  enters  and  leaves 


LIGHTING  AND  LAMPS 


461 


after  making  its  circuit  of  the  room,  is  an  interesting  feature.  The 
length  of  tube  is  suspended  (Fig.  39)  by  brass  clasps,  and  the  light  is 
estimated  from  the  candle-power  per  inch. 


TUBE  SUPPORTED  FROM  WALL 
OR  CEILING 


LIGHT  MEASURED  PER  INCH 
OR  FOOT  OF  TUBE 


FIG.  39. — Vacuum  tube  lighting  in  daily  practice. 

The  power  used  is  alternating,  and  is  transformed  into  a  current 
with  a  particular  form  of  wave.  The  action  of  this  upon  the  gas  in  the 
tube  causes  a  uniform  glow  of  the  pleasantest  character.  No  brilliant 
centre  of  light  appears,  but  a  type  of  diffused  radiance  that  is  highly 
suitable  to  indoor  illumination.  The  efficiency  of  this  system  is 
claimed  to  be  greater  than  that  of  the  incandescent  lamp. 

E L E CTR  I  C -LI  G HT     EQUIPMENTS 

There  are  many  methods  in  use  of  obtaining  systematic  rotation 
in  a  mechanical  sense;  and  it  is  quite  evident  that  rotation  of  this 
character  is  suited  in  every  respect  to  electric  lighting  through  the 
medium  of  the  dynamo.  The  well-known  devices  producing  this  type 
of  power  are  steam-engines  or  turbines,  gas-  or  oil-engines,  and  water- 
wheels.  Each  deserves  separate  consideration  in  a  treatment,  how- 
ever brief,  of  this  subject. 


STEAM      ELECTRIC      PLANTS 

The  consumption  of  steam  in  reciprocating  engines  or  turbines 
obtained  from  boilers  represents  in  total  the  elements  of  a  steam- 
plant.  The  boiler  and  its  accessories,  the  engine  or  turbine,  and 


462 


LIGHTING  AND  LAMPS 


the  generators  and  switchboard,  with  its  light-  or  power-circuits, 
comprise  the  modern  equipment  whose. size  and  character  of  service 
give  it  the  name  of  private  plant,  central  station,  or  power-house. 
The  fact  that  the  electricity  is  consumed  privately,  does  not  necessarily 
limit  the  size  of  the  plant.  A  private  plant  may  be  far  greater  than  a 
central  station,  yet  differ  from  it  in  purpose  and  hours  of  service.  A 
central  station  is  a  public  dispenser  of  light  and  power,  operating  under 
a  municipal  franchise.  -A  power-house,  in  contradistinction,  is  a  street- 
railway  equipment,  sending  out  power  primarily  for  the  cars  along  the 
route,  yet  incidentally  supplying  electricity  for  light  and  power. 

These  three  great  equipments  are  thus  defined  as  the  private  plant, 
however  large,  having  no  franchise;  the  central  station,  generating 
electricity  for  light  and  power  purposes;  and  the  power-house  or  street- 
railway  plant,  whose  franchise  is  directly  intended  to  have  it  serve 
street-railway  interests.  The  general  efficiency  of  these  equipments  is 
dependent  upon  the  character  of  the  boilers,  engines  or  turbines,  and 
generators  in  operation.  The  weight  of  coal  consumed  per  horse- 


COAL  CONSUMED 
EQUALS  100 


MECHANICAL  POWER 
OBTAINED 


ELECTRIC  POWER 
OBTAINED 


S  PER 
CENT 

D 

LIGHT  OBTAINED  BY 
INCANDESCENT  LAMPS 


FIG.  40. — Relative  light  effect  obtained  from  a  given  amount  of  coal  by  electric 
lighting  by  incandescent  lamps. 


power  or  kilowatt  hour  and  the  cost  of  handling  that  power  until  it 
is  paid  for  by  the  consumer  constitute  the  economic  problem  presented 
to  the  manager  of  large  or  small  equipments  of  the  central-station 
class. 

The  range  of  efficiency  for  the  steam,  generating,  and  transmitting 
and  distributing  sections  are  all  well  known,  as  likewise  that  for  the 
various  types  of  lamps.  These  facts  may  be  arranged  (Fig.  40)  in  a 
convenient  form  for  reference. 

1.  The  steam  section  has  an  efficiency  of  from  14  to  16  per  cent, 
from  the  coal  to  the  mechanical  energy  delivered. 


LIGHTING   AND  LAMPS  463 

2.  The  generating  section  has  an  efficiency  of  from  90  to  95  pel 
cent,  from  the  engine  or  turbine  to  the  switchboard. 

3.  The  transmitting  and  distributing  section  has  an  efficiency  of 
from  90  to  95  per  cent,  from  the  switchboard  to  the  consumers'  lights. 

4.  The  illuminating  section,  or  lamps,  have  an  efficiency  of  from 
3  to  10  per  cent,  from  the  circuit  terminals  to  the  candle-power  pro- 
duced.    The  rating  would  be  about  3  per  cent>for  incandescents, 
6  per  cent,  for  Nernst  and  mercury  vapor,  and  about  10  per  cent, 
for  arc-lamps  in  general. 

It  seems  a  very  difficult  matter  at  present  to  generate  light-waves 
without  first  developing  heat-waves,  as,  for  instance,  in  all  the  illu- 
minants  known,  with  the  possible  exception  of  the  vacuum-tube. 
The  making  of  light  is  therefore  restricted  by  the  limit  of  present 
scientific  knowledge.  The  only  gain,  outside  of  the  element  of  depre- 
ciation— which  is  reducible  only  by  strengthening  or  by  reducing  the 
number  of  deteriorating  parts  in  a  plant — is  by  cheapening  the  original 
power-supply.  This  is  a  condition  implied  by  the  fixity  of  the  general 
efficiencies  in  all  but  the  starting-point.  Here  the  water-power 
proposition  becomes  of  interest,  as  well  as  that  concerning  the  develop- 
ment of  power  from  explosive  engines. 

WATER-POWER     PLANTS 

A  stream  of  quickly  flowing  or  falling  water,  developing  enough 
energy  to  move  a  water-wheel  or  turbine  all  the  year  round,  is  an 
interesting  possibility  if  it  is  near  a  city  or  town.  If  many  miles  away 
from  a  large  community,  its  usefulness  will  be  governed  by  its  power. 
It  pays  to  transmit  enough  power  thus  obtained,  if  the  supply  is  com- 
paratively regular.  Otherwise  its  value  is  limited,  as  when  the  supply 
varies  greatly  from  summer  to  winter  or  ceases  altogether  temporarily. 

A  variable  source  of  power  may  mean  an  auxiliary  steam-plant, 
making  the  economic  issue  doubtful  in  the  extreme.  Power  thus 
obtained,  however,  is  cheap  if  regular,  and  simplifies  the  electric-light- 
and-power  proposition,  provided  the  distance  of  transmission  is  not  so 
great  that  the  investment  for  poles,  insulators,  and  conductors  repre- 
sents an  unreasonable  figure. 

A  turbine  or  water-wheel  varies  in  efficiency  from  70  to  85  per  cent. 
The  delivery  of  that  power  at  a  distance  costs,  roughly,  in  proportion 


464 


LIGHTING  AND  LAMPS 


to  the  distance.  This  is  a  problem  best  solved  by  reference  to  exist- 
ing data  concerning  similar  power-transmission  plants.  Hydro-electric 
plants,  as  they  are  called,  really  consist  of  only  the  water-wheel,  the 
generator,  the  switchboard,  and  the  outside  circuits.  Cheap  power 
is  the  natural  consequence  of  an  equipment  of  this  character  if  intel- 
ligently constructed  and  handled. 


GAS-ENGINE   ELECTRIC   PLANTS 

Instead  of  burning  coal  the  process  of  distilling  it  for  its  explosive 
gases,  and  using  them  as  a  source  of  power,  is  becoming  prevalent. 
Small  gas-making  plants  of  this  character  are  called  "gas-producer 
plants."  The  government  tests  show  an  immense  increase  in  fuel- 
efficiency  in  distilling  coal  and  instead  of  burning  the  coal  under  a  boiler, 
exploding  the  gas  to  gain  power  in  a  gas-engine.  The  use  of  so-called 
illuminating-gas  in  a  gas-engine,  and  the  application  of  the  resulting 
power  to  the  production  of  electricity,  is  becoming  more  emphasized  in 
central-station  practice  than  ever  before.  Private  plants  thus  equipped 
are  numerous  on  account  of  the  elimination  of  the  boiler  and  its  acces- 
sories and  the  consequent  simplification  resulting.  If,  instead  of  the 
boiler,  a  gas-producer  plant  is  installed  wherein  the  power-supply  is  to 
be  great  enough,  the  expense  for  gas  is  so  reduced  that  a  kilowatt  hour 
costs  less  than  one-half  of  its  production  in  a  steam-plant  of  equal 
size. 

The  depreciation  of  gas-engines  and  their  accessories  is  therefore 
balanced  up  against  steam-engines  and  their  accessories  in  forming 
a  correct  estimate  of  the  cost  of  operation.  The  capacity,  horse-power, 
speed,  and  weight  of  a  line  of  gas-engine  plants  for  small  installations 
are  given  in  the  following  table,  with  the  form  of  the  manufacturers' 
guarantee : 


Kilo- 
watts. 

Horse- 
power. 

Speed. 

Type. 

Weight 
of  engine. 

Floor- 
space, 
inches. 

Weight  of 
direct- 
connecting 
unit. 

Floor- 
space, 
inches. 

No.  lights, 
16  candle- 
power. 

2* 

6 

400 

Vertical. 

2,050 

36X39 

2,850 

36X64 

50 

7 

12 

360 

2  cylinder. 

3,200 

38X42 

5,700 

38X96 

120 

10 

18 

350 

2  cylinder. 

4,400 

40X44 

7,200 

40  X  102 

180 

20 

30 

300 

2  cylinder. 

8,200 

53X57 

13,500 

53  X  122 

360 

LIGHTING   AND  LAMPS  465 

MANUFACTURERS'  GUARANTEE. 


We  install  these  plants  with  the  guarantee  that  there  will  be  no 
noise  from  the  exhaust.  We  guarantee  every  machine  against 
breakage  or  undue  wear  for  one  year. 


To  recapitulate,  with  reference  to  the  foregoing  facts  the  present 
practice  shows  the  limit  of  power-  and  light-efficiency,  and  indicates,  as 
a  means  of  improving  the  net  efficiency,  the  necessity  for  either  cheap- 
ening the  power  or  changing  the  lighting  system  in  vogue,  not  super- 
ficially, but  fundamentally.  Cheapening  the  power  is  an  obvious 
way,  relatively,  but  this  is  not  true  of  the  light.  It  must  be  under- 
stood that  because  of  the  comparatively  low  efficiency  of  the  light, 
even  of  the  flaming  arc,  it  becomes  imperative  to  make  power  cheaper 
to  cheapen  electric  lighting. 

The  intermediate  machinery  between  the  heat  or  gas-explosion 
and  the  light  will  probably  remain  unchanged  for  some  time.  Progress 
therefore  will  be  best  evidenced  scientifically,  and  subsequently  com- 
mercially, by  the  development  of  a  plan  or  system  by  means  of  which 
the  long  heat-waves  are  cut  entirely  out,  and  the  short  light-waves 
are  produced  with  greater  directness.  This  would  mean  cold  instead 
of  hot  light  at  the  source,  and  an  immense  saving  in  energy  now 
uselessly  and  widely  dissipated. 

QUESTIONS  AND  ANSWERS  ON   CHAPTER  XXIV 

Question. — How  may  the  operation  of  the  dynamo  be  best  de- 
scribed ? 

Answer. — As  the  movement  of  conductors  through  lines  of  force, 
or  the  movement  of  lines  of  force  through  conductors. 

Question. — How  do  the  electromotive  forces  of  a  motor  and  dynamo 
serve  different  purposes? 

Answer. — The  electromotive  force  generated  in  the  armature  of  a 
motor  is  opposite  to  the  electromotive  force  sending  the  current  in, 
and  acts  as  a  regulator.  The  electromotive  force  of  a  dynamo  is 
used  to  send  the  current  through  the  circuits  and  their  resistances. 

Question. — What  is  produced  in  conductors  cutting  lines  of  force, 
or  in  lines  of  force  cutting  conductors? 

Answer. — Electromotive  force  is  produced  within  the  conductors. 


466  QUESTIONS  AND  ANSWERS 

Question. — How  does  the  alternator  and  the  direct-current  gen- 
erator differ? 

Answer. — The  direct-current  generator  uses  a  commutator  in  order 
to  send  out  a  current  flowing  always  in  the  same  direction.  The 
alternating-current  generator  uses  collector-rings,  which  permit  all 
the  alternations  generated  within  the  armature  to  occur  outside  in 
connected  circuits. 

Question. — What  is  the  formula  for  calculating  electromotive  force? 

Answer. — The  volts  generated  equal  lines  of  force  X  revolutions 
of  the  armature  per  second  X  the  armature-conductors  -=-  100,000,000. 

Question. — What  reverses  the  direction  of  a  current  in  a  conductor? 

Answer. — The  fact  that  it  is  being  moved  past  a  north  pole  or  a 
south  pole.  The  electromotive  force  tends  to  send  a  current  in  one 
direction  when  the  conductors  pass  a  north  pole,  and  in  the  reverse 
direction  when  they  pass  a  south  pole. 

Question. — What  is  the  action  of  the  commutator  and  brushes? 

Answer. — To  permit  all  positive  impulses  to  flow  into  one  brush 
or  set  of  brushes,  and  all  negative  impulses  to  flow  into  the  other 
brush  or  other  set  of  brushes. 

Question. — Where  do  the  positive  and  negative  impulses  of  current 
come  from  ? 

Answer. — From  conductors  which  pass  the  north  and  south  poles 
respectively  in  a  two-pole  or  multipolar  field,  and  with  which  commu- 
tator bars  are  connected;  these  bars  transmit  the  positive  and  nega- 
tive currents  to  the  brushes. 

Question. — What  kind  of  current  is  naturally  generated  in  a  two- 
pole  or  multipolar  direct-current  generator? 

Answer. — A  series  of  reversing  electromotive  forces,  or  what  is 
called  an  alternating  current,  which  is  rectified  or  commutated. 

Question. — How  are  dynamos  classified  with  respect  to  the  char- 
acter of  their  currents? 

Answer. — As  alternating-  and  direct-current  generators.  The 
direct-current  machines  are  further  classified  as  series-,  shunt-,  and 
compound-wound  generators. 

Question. — Of  what  use  is  the  transformer? 

Answer. — To  raise  or  lower  the  voltage;  the  volts  are  raised  or 
stepped  up  for  transmission,  and  lowered  or  stepped  down  when  the 
current  is  to  be  distributed. 


QUESTIONS  AND  ANSWERS  467 

Question. — How  is  the  field  regulated,  and  what  is  the  effect 
of  this  regulation  on  the  voltage? 

Answer. — The  field  is  regulated  by  means  of  a  resistance  in  series. 
When  this  resistance  is  increased  or  decreased  the  current  in  the 
fields  decreases  or  increases.  A  more  powerful  field  means  more  lines 
of  force  and  more  volts,  and  a  weaker  field  means  less  lines  of  force 
and  less  volts. 

Question. — Upon  what  principle  does  the  series-wound  dynamo 
regulate  to  preserve  a  constant  current  and  a  varying  potential  ? 

Answer. — Upon  the  principle  that  some  armature-conductors  pro- 
duce more  volts  than  others  when  in  certain  positions  in  the  field.  In 
consequence  the  brushes  may  be  made  to  touch  either  where  the  pres- 
sure is  high  or  low  by  an  automatically  controlling  electromagnet 
in  series  with  the  line. 

Question. — How  is  a  shunt  dynamo  regulated  for  a  constant 
potential  and  a  varying  current? 

Answer. — By  controlling  the  current  entering  the  fields  the  shunt 
dynamo  is  made  stronger  or  weaker,  thus  enabling  the  armature  to 
produce  a  higher  or  a  lower  voltage  to  compensate  for  the  armature- 
reaction  in  the  form  of  drop  and  a  reactive  field. 

Question. — How  is  regulation  accomplished  in  a  compound-wound 
dynamo  to  preserve  a  constant  potential  with  a  varying  current  ? 

Answer. — By  means  of  an  adjunct  coil  in  series  with  the  main  line, 
the  increasing  current  of  the  armature  enables  the  dynamo  to  produce 
more  magnetism.  This  magnetism  is  so  regulated  that  its  increase 
approximately  counterbalances  the  loss  in  magnetism  sustained  by 
the  reactive  effect  of  the  armature.  It  also  supplies  enough  extra 
lines  of  force  to  enable  the  armature  to  generate  as  many  more  volts 
as  are  needed  to  make  up  for  the  drop  within  its  conductors. 


QUESTIONS    AND    ANSWERS    ON    CHAPTER    XXV 

Question. — What  two  cases  are  presented  with  respect  to  grounds  ? 
Answer. — A  ground  in  one  or  more  coils. 
Question. — What  is  the  effect  of  a  heavy  ground? 
Answer. — Heat  in  the  coil  or  coils  thus  affected. 
Question. — How  is  a  short  circuit  explained? 

Answer. — As  a  case  in  which  the  current  enters  a  path  of  lower 
resistance. 


468  QUESTIONS  AND  ANSWERS 

Question. — What  is  done  to  dispel  moisture? 
Answer. — The  coil,  if  possible,  is  carefully  baked. 
Question. — Name  some  of  the  causes  of  sparking. 

Answer. — Among  the  principal  causes  of  sparking  may  be  men- 
tioned: too  great  a  load,  a  wrong  position  of  the  brushes,  loose 
brushes  or  projecting  mica,  a  general  design  that  is  poor  (such  as  a 
badly  proportioned  air-gap),  etc. 

Question. — When  should  a  hard  or  a  soft  brush  be  employed  ? 

Answer. — When  the  commutator  is  hard-drawn  copper  the  carbon- 
brush  should  be  used.  When  the  commutator  is  of  softer  metal  a 
brush  must  be  used  that  will  not  grind  the  commutator  into  metallic 
powder. 

Question. — When  is  sparking  ineradicable? 

Answer. — When  the  design  is  bad,  by  which  is  meant  that  the 
relationship  between  the  thickness  of  the  air-gap,  the  arc  of  the  pole- 
piece,  and  the  load  the  armature  bears,  is  not  correct. 

Question. — At  what  instant  does  sparking  generally  occur? 

Answer. — When  the  conductor  enters  the  lines  of  force  of  a  new 
pole  after  leaving  one  of  opposite  polarity. 

Question. — What  is  the  purpose  of  the  pole-piece  fringe? 
Answer. — To  permit  a  sparkless  reversal  of  the  current. 

Question. — If  the  dynamo  will  not  generate,  what  are  the  causes 
which  may  be  regarded  as  effective? 

Answer. — There  may  be  no  residual  field;  the  magnets  may  have 
the  same  polarity;  the  field-coil  may  have  an  open  circuit;  the  arma- 
ture-connections may  be  open  or  may  be  short-circuited,  etc. 

Question. — What  causes  black  bars  in  the  commutator? 

Answer. — A  broken  coil  in  the  armature  causes  black  bars  between 
the  ends  of  the  break. 

Question.— What  are  the  causes  of  a  hot  armature  ? 

Answer. — An  overload,  short-circuited  coils  on  the  armature, 
and  very  thick  conductors. 

Question. — What  are  the  types  of  direct-current  motors  that  are 
in  use? 

Answer. — The  series,  the  shunt,  and  the  compound  wound. 


QUESTIONS  AND  ANSWERS  469 

Question. — What  causes  heat  in  the  commutator? 

Answer. — Bad  contact  between  the  brushes  and  the  commutator, 
a  small  commutator,  too  much  pressure  from  the  brushes,  or  a  brush 
of  too  great  a  resistance. 

Question. — What  is  the  effect  of  increasing  or  diminishing  the 
current? 

Answer. — The  heat  varies  as  the  square  of  the  current  in  amperes. 
Twice  the  amperes  means  four  times  the  heat,  three  times  the  amperes 
nine  times  the  heat,  etc. 

Question. — What  general  rule  may  be  depended  upon  with  regard 
to  heated  bodies,  whether  heated  by  electricity  or  by  any  other  means  ? 

Answer. — That  the  amount  of  external  or  radiating  surface  will 
govern  the  rise  of  temperature  with  any  steady  supply  of  heat. 

Question. — In  what  important  respect  do  steam  and  electrical 
practice  differ? 

Answer. — In  steam  practice  the  effort  is  made  to  prevent  the  heat 
from  radiating;  in  electrical  practice  the  radiation  of  the  heat  from 
conductors  is  obligatory. 

Question. — What  will  happen  to  a  series  motor  with  no  load? 
Answer. — It  will  wreck  itself  by  attaining  a  destructive  speed. 
Question. — How  is  a  shunt-wound  motor  started  up? 

Answer. — Always  with  the  field  full  on,  and  a  rheostat  in  series 
with  the  armature. 

Question. — What  is  the  purpose  of  a  compound  winding  in  a  motor  ? 

Answer. — To  either  strengthen  the  field,  or  weaken  it  with  a  heavy 
load. 

Question. — With  what  effect  will  a  stronger  or  a  weaker  field 
operate,  and  what  are  their  uses? 

Answer. — A  stronger  field  makes  a  shunt  motor  run  slower,  and  a 
weaker  field  faster,  with  a  given  load.  A  compound  winding  permits 
this  through  the  influence  of  the  series  coil,  which  may  be  connected 
so  as  to  strengthen  or  weaken  the  field. 

Question. — What  is  the  value  of  the  back  electromotive  force 
of  a  motor? 

Answer. — It  is  equal  to  the  difference  between  the  impressed 
electromotive  force  and  the  voltage  required  to  send  the  amperes  at 
any  particular  point  of  load  through  the  armature. 


470  QUESTIONS   AND  ANSWERS 

Question. — What  is  the  difference  in  a  direct-current  motor  be- 
tween doing  the  greatest  possible  amount  of  work  and  having  a  high 
efficiency? 

Answer. — When  making  the  motor  do  its  greatest  possible  work 
it  will  be  overloaded,  run  slowly,  and  thus  develop  power  at  a  very 
low  efficiency. 

Question. — What  is  an  indication  of  an  open  circuit  in  the  arma- 
ture? 

Answer. — A  high  speed,  a  line  of  sparks  or  two  burnt  bars. 
Question. — What  is  the  back  electromotive  force  of  a  motor? 

Answer. — The  electromotive  force  developed  by  the  armature- 
conductors  cutting  the  lines  of  force. 

Question. — What  is  the  electrical  efficiency  of  a  motor? 

Answer. — The  ratio  between  the  back  and  the  impressed  electro- 
motive force. 

Question. — What  is  the  commercial  efficiency  of  a  motor? 

Answer. — The  ratio  between  the  mechanical  power  taken  out 
and  the  electrical  power  sent  in. 

Question. — What  are  the  causes  of  noise  in  motors? 

Answer. — The  armature-slots  and  the  pole-tips,  the  brush  on 
the  commutator  not  being  properly  inclined,  a  rough  commutator, 
and  lack  of  lubrication. 

QUESTIONS  AND  ANSWERS  ON  CHAPTER  XXVI 

Question. — What  is  meant  by  the  term  "switchboard"  ? 

Answer. — Technically  a  board  on  which  switches,  protective 
apparatus,  measuring-instruments,  etc.,  are  found,  and  by  means  of 
which  the  entire  system  is  operated. 

Question. — What  are  the  classes  of  devices  found  on  a  switchboard? 

Answer. — Measuring-instruments,  controlling  devices,  protective 
devices,  regulating  devices,  and  testing  devices. 

Question. — How  are  the  circuits  classified? 

Answer. — As  mains,  feeders,  branches,  and  sub-branches. 

Question. — What  is  a  centre  of  distribution? 

Answer. — A  point  on  each  floor,  or  group  of  floors,  from  which 
control  over  those  particular  circuits  may  be  exercised. 


QUESTIONS  AND  ANSWERS  471 

Question. — What  is  meant  by  the  term  "panel  board"? 

Answer. — Small  boards  set  in  the  wall  that  are  supplied  with 
switches  and  fuses  for  a  given  group  of  circuits. 

Question. — What  fundamental  form  of  protection  must  be  supplied 
to  circuits  in  all  cases? 

Answer. — Protection  against  overflows  of  current  in  the  form  of 
fuses  or  circuit-breakers. 

Question. — What  are  the  natural  parts  or  sections  into  which  a 
switchboard  may  be  subdivided? 

Answer. — Generating,  feeding,  and  metering  sections. 
Question. — What  do  the  ammeter  and  voltmeter  indicate? 

Answer. — The  ammeter  indicates  the  extent  of  the  load  on  the 
dynamo.  The  voltmeter  indicates  the  pressure  at  which  the  current 
is  supplied. 

Question.— How  do  these  two  instruments  differ  in  design? 

Answer. — The  ammeter  is  made  of  as  low  a  resistance  as  possible, 
the  voltmeter  of  as  high  a  resistance  as  possible. 

Question. — How  are  ammeters  and  voltmeters  connected  up  in 
circuit? 

Answer. — The  ammeter  is  always  placed  in  series  with  the  load, 
the  voltmeter  always  in  multiple. 

Question. — Of  what  purpose  is  a  wattmeter  in  a  circuit? 

Answer. — It  indicates  the  total  of  power  used  in  any  period  of 
time,  as  given  in  watts  or  kilowatt  hours. 

Question. — How  does  the  circuit-breaker  operate? 

Answer. — It  opens  the  circuit  abruptly  through  the  medium  of  a 
switch  and  controlling  electromagnet,  when  the  current  reaches  a 
given  value  to  which  the  magnet  is  set  to  operate. 

Question. — What  governs  the  action  of  a  lightning-arrester? 

Answer. — The  oscillatory  nature  of  the  discharge,  through  which 
it  finds  less  resistance  in  an  air-gap  than  a  conductor  under  certain 
conditions. 

Question. — What  is  a  ground-detector? 

Answer. — A  device  by  means  of  which  the  contact  between  a 
.  leg  of  the  circuit,  or  both  legs,  and  the  earth,  directly  or  indirectly, 
is  indicated. 


472  QUESTIONS  AND  ANSWERS 

Question. — What  would  be  the  result  of  a  heavy  double  ground  ? 

Answer. — A  heavy  double  ground  is  the  equivalent  of  a  short 
circuit.  If  not  heavy,  it  constitutes  a  source  of  leakage  under  normal 
conditions. 

Question. — What  is  the  storage-cell  used  for? 

Answer. — For  the  purpose  of  creating  a  higher  average  load-line  in 
lighting  and  power  service.  It  also  serves  to  temporarily  increase 
the  capacity  of  the  plant. 

Question. — What  are  the  two  types  of  storage-cell  that  are  em- 
ployed? 

Answer. — The  lead  plate  or  Plante  and  the  pasted  grid  or  Faure 
type. 

Question. — With  which  plates  are  the  positive  and  with  which 
the  negative  pole  of  the  generator  connected? 

Answer. — The  positive  pole  is  always  connected  with  the  reddish 
plates,  and  the  negative  pole  with  the  gray  plates. 

Question. — What  is  the  nature  of  the  solution  employed? 
Answer. — A  20-per-cent.  sulphuric-acid  solution. 

Question. — What  is  the  meaning  of  capacity  in  a  storage-battery? 

Answer. — The  capacity  as  measured  in  ampere-hours,  or  the  num- 
ber of  amperes  of  current  for  a  certain  number  of  hours. 

Question. — Which  is  better,  a  low  or  a  high  rate  of  discharge  from 
a  storage-battery? 

Answer. — A  low  rate  is  better  than  a  high,  as  the  durability  of  a 
stationary  plant  is  thus  increased. 

Question. — What  are  the  main  difficulties  with  storage-cells? 

Answer. — Weight  (if  used  for  locomotion),  sulphating,  and  buck- 
ling. 

Question. — What  is  the  cause  of  sulphating  and  of  buckling? 

Answer. — Sulphating  is  due  to  the  discharged  plates  being  left  in 
the  acid  solution  too  long  uncharged.  Buckling  is  due  to  the  warping 
or  twisting  of  the  plates  if  too  thin  or  if  the  discharge  is  too  heavy. 

Question. — What  is  the  efficiency  of  a  storage-cell? 

Answer. — The  percentage  obtained  by  dividing  the  watts  taken 
out  by  the  watts  sent  in. 


QUESTIONS  AND  ANSWERS  473 

Question. — Which  would  govern  the  choice  of  a  certain  type 
of  cell,  high  efficiency  and  weakness  or  lower  efficiency  and  greater 
durability? 

Answer. — The  durability  of  the  cell  means  a  greater  advantage 
than  its  higher  efficiency  without  it. 

Question. — What  governs  the  design  of  a  battery-room? 

Answer. — Ventilation,  drainage,  heating,  water-supply,  aisle- 
space,  floor-construction,  and  no  metal-work. 

Question. — How  does  cold  affect  the  cell-capacity? 

Answer. — It  lowers  its  capacity,  and  for  that  reason  the  battery- 
room  must  be  kept  reasonably  warm. 

Question. — What  paint  is  durable  in  a  battery-room? 

Answer. — Asphaltum  paint,  or  a  paint  not  affected  by  acid  or  the 
fumes  of  charging. 

Question. — How  should  the  cells  be  arranged? 

Answer. — They  are  best  arranged  in  tiers  one  above  the  other, 
with  plenty  of  space  for  lifting  out  or  examining  the  cells. 

QUESTIONS  AND  ANSWERS  ON  CHAPTER  XXVII 

Question. — How  are  electric  lamps  classified? 

Answer. — As  incandescent,  arc,  mercury  vapor,  and  vacuum  tube, 
which,  with  their  variations,  include  the  total  field. 

Question. — What  are  the  two  most  prominent  types  of  lamps  in 
use? 

Answer. — The  incandescent  with  carbon  filament,  and  the  arc  of 
the  enclosed  and  the  open  type. 

Question. — What  are  the  features  of  importance  in  the  so-called 
flaming-arc  lamp? 

Answer. — The  use  of  an  impregnated  and  cored  carbon  and  the 
greater  extension  of  the  arc  so  as  to  give  greater  illumination. 

Question. — How  is  the  modern  lamp-filament  made? 

Answer. — By  the  carbonization  of  a  fine  thread  of  cellulose,  to 
which  are  attached  platinum  leading-in  wires  sealed  in  a  glass  stem. 

Question. — How  are  lamps  rated? 

Answer. — By  the  watts  or  power  consumed  per  candle-power. 


474  QUESTIONS  AND  ANSWERS 

Question.— Why  is  platinum  employed  as  leading-in  wires? 

Answer. — Because  the  platinum  expands  and  contracts  at  the 
same  rate  as  the  glass,  and  thus  preserves  the  vacuum. 

Question. — What  are  the  three  elements  to  consider  in  lamps? 
Answer. — The  cost,  durability,  and  efficiency. 

Question. — What  is  the  difference  between  old  lamps  in  service 
and  new? 

Answer. — New  lamps  take  less  watts  per  candle-power  than  old 
ones.  The  older  a  lamp  the  more  watts  consumed  per  candle-power; 
hence  old  lamps  are  less  efficient  and  more  wasteful  commercially 
than  new. 

Question. — How  does  the  light  of  an  arc-lamp  compare  with  that 
of  an  incandescent  lamp  from  the  standpoint  of  efficiency  and  candle- 
power  ? 

Answer. — An  incandescent  lamp  takes  about  3  to  3.5  watts  per 
candle-power;  therefore  1,000  candle-power  obtained  in  this  manner 
means  a  consumption  of  from  3,000  to  3,500  watts.  An  arc-lamp 
takes  about  600  watts  to  deliver  about  1,200  candle-power,  or  J  watt, 
or  even  less,  per  candle-power,  depending  upon  the  type  of  lamp. 
On  this  basis  1,000  candle-power  by  incandescent  means  at  least  3,000 
watts  consumed;  by  arc  it  means  about  500  watts  consumed. 

Question. — What  is  a  Nernst  lamp? 

Answer. — A  lamp  in  which  a  piece  of  rare  oxide  is  raised  to  in- 
candescence by  means  of  a  current. 

Question. — Wherein  does  a  Nernst  lamp  possess  advantages  over 
the  carbon  filament? 

Answer. — In  the  fact  that  it  can  be  safely  raised  to  a  higher  tem- 
perature; also  in  the  fact  that  no  vacuum  is  necessary. 

Question. — What  is  an  open  arc? 

Answer. — An  arc-lamp  whose  carbons  burn  in  the  open  air. 

Question. — How  are  open-arc  lamps  connected  up? 
Answer. — Generally  as  two  in  series  on  a  110-  or  115-volt  line. 

Question. — How  are  they  connected  on  high-tension  arc-lines? 

Answer. — In  series  throughout  the  system.  An  allowance  of 
about  50  volts  per  lamp  is  made,  which  would  mean  at  least  forty 
open  arcs  in  series  on  a  2,000-volt  system. 


QUESTIONS  AND  ANSWERS  475 

Question. — What  are  the  features  of  the  flaming-arc  lamp? 

Answer. — It  produces  a  more  efficient  light  than  other  arcs;  it 
throws  off  deleterious  gases;  its  carbons  must  be  renewed  every  ten 
or  fifteen  hours;  its  carbons  are  set  at  an  angle  to  each  other;  the 
flame  gives  out  light  as  well  as  the  tips. 

Question. — What  are  the  features  of  the  enclosed-arc  lamp? 

Answer. — It  will  burn  100  to  150  hours  without  attention  or 
carbon-renewals;  it  takes  more  power  than  an  open  arc;  its  carbons 
last  because  the  oxygen  in  the  small  globe  surrounding  the  tips  is 
consumed,  and  a  valve  prevents  more  air  from  entering  freely. 

Question. — What  defects  appear  in  the  enclosed  arc? 

Answer. — The  deposits  on  the  inner  globe  cut  down  the  light,  and 
the  separation  of  the  carbons  calls  for  a  higher  pressure  than  the  open 
arc,  a  pressure  of  from  80  to  100  volts  being  required.  This  means 
only  one  lamp  on  a  110-  or  115-volt  line,  and  power  wasted  in  the  resist- 
ance necessary  to  limit  the  current. 

Question. — What  is  a  mercury-vapor  lamp? 

Answer. — A  lamp  formed  by  a  tube  with  terminal  electrodes, 
and  containing  a  small  quantity  of  mercury.  By  tilting  the  tube  the 
mercury  connects  the  electrodes,  vaporizes,  and  forms  a  band  of  daz- 
zling light. 

Question. — What  are  its  features  in  practice? 

Answer. — The  production  of  a  form  of  light  without  any  red  rays, 
a  high  efficiency,  an  automatic  device  for  tilting  it  to  start  the  arc. 

Question. — What  is  a  vacuum-tube  system  of  lighting? 

Answer. — At  present  it  means  a  long  tube  of  50,  100,  or  150  feet, 
containing  a  gas  which,  when  affected  by  a  high-pressure  alternating 
current,  produces  commercial  lighting  effects.  It  originally  repre- 
sented a  tube  containing  a  vacuum,  with  electrodes  by  which  the 
residuum  of  air  caused  illumination  by  molecular  bombardment. 

Question. — What  are  its  features? 

Answer. — An  efficiency  claimed  to  be  that  of  the  incandescent 
lamp,  no  deterioration  of  any  consequence,  ready  installation,  no 
glare,  but  a  uniform  glow. 

Question. — What  are  the  sources  of  power  employed  for  electric 
lighting? 

Answer. — Steam,  gas,  oil,  water,  and  in  some  instances  the  sun 
or  the  wind. 


476  QUESTIONS  AND  ANSWERS 

Question. — What  are  the  elements  of  an  electric-light  plant? 

Answer. — The  boiler  and  its  accessories,  the  engine  or  turbine, 
the  switchboard,  and  the  circuits  inside  and  outside  used  for  distribu- 
tion and  transmission. 

Question: — What  is  a  private  plant,  a  central  station,  and  a  power- 
house ? 

Answer. — A  private  plant  supplies  current  to  a  building  or  buildings 
and  grounds,  without  any  sale  of  current  taking  place  or  any  municipal 
relationship  being  involved.  A  central  station  has  as  its  primary 
purpose  the  sale  of  current  under  a  franchise  granted  by  the  com- 
munity to  be  supplied.  A  power-house  is  generally  representative 
of  a  plant  supplying  street-railway  power  to  a  trolley-line.  It  may 
be  the  distributing  centre  of  a  transmission-plant  miles  away. 

Question. — Into  what  sections  may  a  plant  of  public  or  private 
utility  be  divided? 

Answer. — Into  the  steam  section  or  power-developing  element, 
the  generating  section,  the  transmitting  and  distributing  section,  and 
the  illuminating  and  motive-power  section. 

.Question. — What  is  the  great  difficulty  with  our  present  method 
of  light- production? 

Answer. — The  method  of  generating  heat-waves  in  order  to  reach 
the  light-waves  required. 

Question. — What  are  the  advantages,  in  an  economic  sense,  of 
a  water-power  source  instead  of  steam? 

Answer. — The  limited  cost  of  the  power,  provided  it  can  be  de- 
pended upon  throughout  the  year,  and  the  high  efficiency  of  the  water- 
wheel. 

Question. — What  is  the  economic  disadvantage  of  a  water-power 
plant? 

Answer. — The  limited  value  of  the  water-power  due  to  its  great 
distance  from  the  community,  and  the  cost  of  transmission,  even 
though  the  power  is  regular,  eliminating  the  gain  otherwise  in  evi- 
dence. 

Question. — What  are  the  advantages  of  producer  gas  in  electric- 
light  plants? 

Answer. — The  use  of  the  fuel  in  such  a  manner  that  the  electricity 
produced  is  cheaper  than  by  means  of  direct  combustion  for  steam. 
No  boiler  is  required,  but  a  gas-producing  plant,  which  distills  the 


QUESTIONS  AND  ANSWERS  477 

coal  or  other  fuel,  and  the  gas  thus  obtained  is  exploded  in  a  gas- 
engine.  Instead  of  heat  and  steam-power,  use  is  made  of  gas  and 
the  explosive  force  latent  when  mixed  with  air. 

Question. — What  is  the  drift  of  engineering  practice  in  the  lighting 
field? 

Answer. — The  production  of  cheaper  power,  in  order  to  not  only 
cheapen  the  cost  of  light,  but  increase  the  quantity  in  use  per  capita. 

Question. — What  is  the  tendency  in  scientific  light-making? 

Answer. — To  attempt  the  production  of  light  that  possesses  no 
preliminary  heat-waves,  in  order  to  gain  an  efficiency  that  will  in- 
crease the  amount  of  light  obtainable  from  a  given  power-consumption 
many  fold.  Where  an  incandescent  lamp  wastes  97  per  cent,  in  heat, 
and  gives  out  only  3  per  cent,  in  light,  the  elimination  of  the  heat- 
element  would  mean  theoretically  33  X 16,  or  528  candle-power  instead 
of  only  16  candle-power  for  a  watt  consumption  of  50. 


INDEX 


*  For  Index  to  Electrical  Section,  see  page  485. 


Acceleration  of  steam  in  nozles,  141. 
Actual  efficiency,  181. 
Adiabatic  expansion  of  steam,  171. 
Air-  and  circulating-pump,  126. 
Air-compressors,  385-389. 
Air  for  furnaces,  82,  83. 
Air,  hot,  for  furnaces,  83. 
Air-pumps,  126,  127. 
American    Company's  compound  en- 
gine, 297. 

Ammonia,  charging  and  starting,  370. 
Ammonia-compressor,  356. 
Ammonia-condensers,  361-363. 
Ammonia-cylinders,  359-361. 
Ammonia-plant,  operation  of,  364. 
Angle  of  connecting-rod,  231. 
Anhydrous  ammonia,  349. 
Automatic  elevator-governor,  377. 
Available  heat,  exhaust,  175. 
Available  heat,  steam,  175. 
Avery  turbine,  317,  318. 

B 

Back  pressure,  182. 

Balanced  valves,  239,  240. 

Blowing-engine,  388. 

Boiler,  Babcock  &  Wilcox,  59. 

Boiler-braces,  71,  72. 

Boiler,  Cahall,  56. 

Boiler-chimney  and  its  work,  74-85. 

Boiler,  cylinder,  49. 

Boiler,  cylinder  tubular,  50-52. 

Boiler,  double-flue,  50. 

Boiler,  down-draught,  54. 


Boiler,  duplex,  56. 

Boiler,  Du  Temple,  55. 

Boiler-furnaces,  31-48. 

Boiler,  Galloway,  50. 

Boiler,  heating  and  grate-surface  of,  62. 

Boiler,  Herreshoff,  54. 

Boiler  horse-power,  61,  62,  184. 

Boiler-joints,  68-72. 

Boiler,  marine,  33. 

Boiler,  Robb-Mumford,  53. 

Boiler-setting,  51,  52. 

Boiler,  Sterling,  57,  58. 

Boiler,  Stevens,  49. 

Boiler,  strength  of,  67-73. 

Boiler,  Thornycroft,  54. 

Boiler,  vertical,  60. 

Boiler,  Wood,  55. 

Boiler,  Worthington,  41. 

Boilers,  41,  49-61. 

Boiling  in  vacuo,  28-30. 

Boiling-point  of  pure  water,  26. 

Boiling-point  of  solutions,  27. 

Burners,  oil,  steam,  and  air,  46-48. 


Cable-elevator,  372. 
Charging  ammonia-plant,  370. 
Chimney-draught,  81-83. 
Chimneys,  75-80. 
Chimneys,  steel  and  brick,  79. 
Coal,  progress  in  saving,  22. 
Combustion,  34,  35. 
Compound   engines,    292-307. 
Compression,  176,  182,  274. 
Compression  and  admission-lines,  204. 
479 


480 


INDEX 


Compression,  excessive,  183. 
Compressors,  air,  385-389. 
Condensation,  initial,  208,  292. 
Condenser,  siphon,  119,  120. 
Condenser-surface,  123-125. 
Condensers,  118-125. 
Condensers,  ejector,  121. 
Condensers,  jet,  121. 
Connecting-rod  angle,  231. 
Cooling-towers,  127,  128. 
Corliss  engine,  267-270,  289. 
Corliss  valve-gear,  270-279. 
Cost  of  power,  390-392. 
Cost  of  superheating,  150. 


Curtiss  steam-turbine,  332. 
Curves  of  nozles,  144. 
Cut-off,  economical  point  of,  188. 
Cut-off,  point  of,  274,  275. 
Cylinder-condensation,  155,  173,  292. 
Cylinder  dimensions,  209,  222. 
Cylinder  ratios,  210. 

D 

Dashpot-governor,  284. 

Dashpots,  285,  286. 

De  Laval  turbine,  320-323. 

Denys  Papin,  16. 

Details  of  elevator-operation,  379. 

Diagram,  ammonia-compression,  363. 

Diagram,  chimney-draught,  75. 

Diagram,  compression  and  expansion 

of  air,  384. 

Diagram,  ideal  and  actual  curves,  187. 
Diagram  of  economical  cut-off,  188. 
Diagram  of  refrigeration,  354. 
Diagram  of  steam-generation,  131. 
Diagram  of  steam  used,  201,  202. 
Diagram,  pressures  and  temperatures, 

310. 

Diagram,  turbine  efficiency,  322. 
Diagram,  turbine  pressure,  332. 
Diagram,  two-stage  compression,  384. 
Diagrams,  efficiency,  302,  303. 


Diagrams,  indicator,  299-301. 
Diagrams,  operating  expenses,  392. 
Diagrams,  receiver,  304,  305. 
Diagrams,  slide-valve,  247,  248. 
Diverging-nozles,  142. 
Don'ts  for  engineers  and  firemen,  401. 
Dow  turbine,  324. 
Draught-gauge,  76. 
Draught-pressure  in  chimneys,  75,  76. 
Dryness  of  steam,  x-,  143,  144. 
Dry  steam,  131,  144. 
D  slide-valve,  233-250. 
Duplex  compound  engine,  298,  299. 
Duplex  cross  compound  Corliss,  14. 
Duplex-piston  engine,  316. 
Duty-test,     triple-expansion     engine, 
309. 

E 

Eccentrics,  shifting,  282,  283. 
Economical  point  of  cut-off,  188. 
Economical  suggestions  in  the  use  of 

steam  for  power,  394-399. 
Economy  in  heating  feed-water,  84. 
Economy  in  high-speed  engine,  1 77. 
Economy  in  refrigeration,  365. 
Economy  of  fuel,  22. 
Efficiency,  actual,  181. 
Efficiency  diagrams,  302,  303. 
Efficiency,  engine-,  180. 
Efficiency  of  heat-engine,  151. 
Efficiency  of  oil-fuel,  45. 
Efficiency-test,  309. 
Efficiency,  turbine-,  322. 
Elevator  and  its  work,  372-389. 
Elevator  pilot- valves,  376. 
Elevator-plant,  375. 
Elevator-ramp,  380. 
Elevator  safety-devices,  378. 
Elevator  worm-gear,   381. 
Energy  of  steam,  145. 
Engine,  Ball  Engine  Company,  264. 
Engine  connecting-rods,  216,  227. 
Engine,  Corliss,  267-270. 
Engine  cross-head,  215,  224-226. 


INDEX 


481 


Engine  details,  208-231. 
Engine-economy,  293. 
Engine  fly-wheel,  222,  229. 
Engine,  knocking  and  other  noises,  401. 
Engine  main  bearings,  220,  227. 
Engine-piston,  213,  223-225. 
Engine,  Porter- Allen,  262. 
Engine,  rotary,  258,  343. 
Engine,  Westinghouse,  300. 
Engines,  compound,  292-307. 
Engines,  right-  and  left-hand,  291. 
Engines,  three-cylinder,  258. 
Engineer  and  his  duties,  400-403. 
Eolipile,  15. 

Erratic  admission-lines,  205. 
Escalator,  381. 
Evaporation  factor,  116. 
Evaporation  of  water,  27,  28. 
Excessive  compression,  183. 
Exhaust-lap  change,  239. 
Exhaust-lines,  erratic,  207. 
Expanding-nozle,  143,  144. 
Expansion,  rule,  178. 
Exponent  of  expansion,  171. 


Factors  of  evaporation,  117. 

Faulty  valve-setting  lines,  206. 

Feed-pipe,  67. 

Feed- water  heaters,  86-93. 

Feed-water,  heating,  84,  85. 

Fitchburg  governor,  283. 

Floating  valve-gear,  257. 

Flow  of  steam   through  orifices  and 

nozles,  140. 

Flow  of  steam  through  pipes,  145. 
Fly-ball  governors,  280,  281. 
Fly-wheels,  222,  230. 
Forced  draught,  80,  82. 
Friction  of  steam,  146. 
Fuel,  cost  of,  34. 
Fuel  for  superheating,  155. 
Fuels,  31-35. 
Furnace-blowers,  81,  82. 
Fusible  plug,  67. 


Gain  by  high  pressure,  185. 
Gases  in  chimney,  35. 
Gauge,  pressure-,  66. 
Gauge,  water-,  63,  65. 
Generation  of  steam,  31-48. 
Governor,  turbine-,  331. 
Governors  andjiashpots,  279. 
Grate-bars,  36.  " 
Grates,  traveling,  39,  40. 
Gridiron  valves,  245,  246. 

H 

Harrisburg  engine,  294. 

Heater,  Berryman,  88. 

Heater,  filter,  90. 

Heater,  Green,  92. 

Heater,  Hoppes,  91. 

Heater,  multicoil,  86. 

Heater,  open,  87. 

Heater,  Wainwright-Cookson,  89. 

Heating  power  of  fuels,  43. 

High-lift   elevator,   375. 

High-pressure,  gain,  186. 

High-pressure  steam,  184. 

Horizontal-plunger   elevator,    376. 

Hornblower's  engine,  19. 

Horse-power,  145. 

Horse-power  from  indicator-card,  200. 

Horse-power  rating  of  boilers,  61,  62. 


Ideal  efficiency,  151. 
Illustrated  superheaters,   160-170. 
Incrustation  and  remedy,  111-116. 
Indicator  and  its  work,  190-207. 
Indicator-cards,  195,  201,  299,  301. 
Indicator-connections,   192-194. 
Indicator-kinks,  203-207. 
Indicator-measurement,  195. 
Indicators  of  boiler-control,  63. 
Initial   condensation,   208. 
Injector-efficiency,  98. 


482 


INDEX 


Injector,  Korting,  and  exhaust,  97. 
Injector,  Little  Giant,  96. 
Injector,  Lunkenheimer,  96. 
Injector,  Metropolitan,  97. 
Injector,  Penberthy,  95. 
Injectors  and  steam-pump,  94-110. 

K 

Kinks  in  indicator-cards,  203-207. 
Knocking  in  the  engine,  401. 


Lane  &  Bodley  govern  or,.  281. 
Lap  and  lead,  237,  238. 
Lap,  lead,  and  exhaust,  289. 
Latent  heat  of  water,  132. 
Leakage-waste,  179. 
Link  valve-gear,  253,  254. 
Loss  in  expansion,  186. 

M 

Marshall  valve-gear,  255. 
Mean  forward  pressure,  173. 
Measurement,  indicator-,  195. 
Measurement  of  steam,  169. 
Mechanical  refrigeration,  348. 
Mechanical  stokers,  37-42. 
Minnesota  engines,  315. 
Montana  engines,  311-313. 
Multiple  expansion,  310,  311. 

N 

Natural  gas  fuel,  33,  34. 
Newcomen's  engine,  17. 
Nozles,  steam-,  141,  142. 

O 

Object  of  superheating,  149. 

Oil-burners,  46-48. 

Oil-fuel,  43-45. 

Oscillating  valve,  244. 

"Over"  and  "under  run"  engines,  235. 


Parson's  turbine,  325-330. 

Petroleum-burners,  46-48. 

Petroleum-fuel,  33,  43-46. 

Pilot- valve,  331. 

Piston-  and  crank-stroke,  231. 

Piston-valves,  251,  252. 

Planimeter,  196-198. 

Pointers  on  refrigeration,  364. 

Port-opening,  236. 

Porter- Allen  governor,  280. 

Pressure-gauge,  66. 

Progress,  diagram  of,  22. 

Progress  in  efficiency,  22. 

Proportions,  steam-engine,  208-223. 

Pump,  Blake,  107,  108. 

Pump,  Cameron,  103. 

Pump,  Deane,  101,  109. 

Pump,  Guild   &  Garrison,  106,  107. 

Pump,  Knowles,  100. 

Pump-lift,  99. 

Pump,  McGowan,  104. 

Pump-proportions,  99. 

Pump-strainer,  109. 

Pump  valve-gear,  102. 

Pump,  Worthington,  101. 

Purification  of  feed-water,   111. 

Purifying  apparatus,   113-116. 

Q 

Quality  of  steam,  x,  144. 
Questions  and  Answers,  403-415. 

R 

Rateau  turbine,  339,  340. 
Ratio  of  expansion,  186. 
Receivers,  304-306. 
Recording-gauge,  66. 
Reducing- wheel,  190,  191. 
Refrigerating-plant,  358. 
Refrigeration-engineering,  348-371. 
Refrigeration  stages,  357. 
Reheating,  306,  307. 


INDEX 


483 


Reheating  steam  in  receivers,  150. 
Release-lines,  206. 


Safety-valve,  63-65. 

Sale  of  steam,  170. 

Salt-evaporating  pan,  28. 

Saturated  steam,  131. 

Saving  by  superheat,  154. 

Scottdale  governor,  282. 

Separators,  oil-,  126. 

Setting  Corliss  valve-gear,  286. 

Shifting  eccentrics,  282. 

Simple  valve-gear,  234. 

Slide-valve  and  gear,  233-266. 

Slide-valves,  balanced,  240. 

Slide-valves,  double-ported,  241. 

Slide-valves,  gridiron,  245,  246. 

Slide-valves,  independent  cut-off,  241. 

Slide-valves,  riding-cover,  240. 

Specific  heat  of  steam,  132,  154, 
158. 

Specific  heat  of  water,  132. 

Steam  above  atmospheric  pressure, 
130. 

Steam  and  its  properties,  24. 

Steam  at  1,000  pounds  pressure,  293. 

Steam  consumption,  302,  303. 

Steam-engine  proportions,  208,  223. 

Steam-exhaust  for  heating,  399. 

Steam-gun,  18. 

Steam-jets  and  -orifices,  140. 

Steam-lines,  205. 

Steam-plant,  starting,  343. 

Steam-pump,  98-110. 

Steam-tables,  135-139. 

Steam-turbines,  317-347. 

Steam  used  from  diagram,  201,  202. 

Steam-waste,  leakage  of,  179. 

Steaming  power  of  boilers,  49-60. 

Stokers,  37-42. 

Sugar -evaporating  plant,  29. 

Suggestions  for  economical  steam- 
generation,  394-399. 


Superheat-economy,  147. 
Superheated  steam,  131,  147-170. 
Superheaters,  159-170. 
Sweet  governor,  283. 


Table  I.  Boiling  below  atmospheric 
pressure,  25.  ~- 

Table  II.     Elastic  force  of  vapor,  25. 

Table  III.  Boiling-point  of  pure 
water,  26. 

Table  IV.  Heat  required  for  evapora- 
tion, 27. 

Table  V.     Fuel  values,  32. 

Table  VI.  Heating  and  grate-sur- 
face, 62. 

Table  VII.  Pressures  and  areas,  safe- 
ty-valves, 64. 

Table  VIII.  Proportions,  boiler-joints, 
69. 

Table  IX.     Safe  pressures,  boilers,  70. 

Table  X.     Stays  for  boilers,  73. 

Table  XI.  Draught  pressures,  chim- 
ney-, 76. 

Table  XII.  Size  and  height  of  chim- 
neys, 77. 

Table  XIII.  Heat-saving  in  feed- 
water,  84. 

Table  XIV.     Feed-water  heaters,  85. 

Table  XV.     Injector-discharge,  95. 

Table  XVI.     Pump-lift  height,  99. 

Table  XVII.  Causes  of  incrustation, 
112. 

Table  XVIII.  Factors  of  evapora- 
tion, 117. 

Table  XIX.  Water  for  condensing, 
123. 

Table  XX.     Properties  of  steam,  135. 

Table  XXI.  Steam-jet  velocities, 
144. 

Table  XXII.  Flow  of  steam  through 
pipes,  146. 

Table  XXIII.  Specific  volumes,  super- 
heat, 152. 


484 


INDEX 


Table  XXIV.       Steam-consumption, 

superheat,  153. 
Table   XXV.     Total   heat   of   steam, 

159. 

Table  XXVI.     Real  -cut-off,  172. 
Table  XXVII.     Mean  forward  pres- 
sure, 174. 
Table   XXVIII.     Terminal   pressure, 

175. 

Table  XXIX.    Heat-efficiency,  181. 
Table    XXX.     Cylinder    dimensions, 

222. 
Table   XXXI.     Cylinder   dimensions, 

223. 
Table    XXXII.      Fly-wheel     speeds, 

230. 

Table  XXXIII.     Effect  of  changing 
lap,   travel,   and  angular  advance, 
238. 
Table  XXXIV.     Lap,  lead,  exhaust, 

289. 

Table  XXXV.  Loss  by  cylinder-con- 
densation, 292. 

Table  XXXVI.  Water-consumption 
in  compound  and  single-cylinder 
engines,  293. 

Table  XXXVII.  Cylinder-propor- 
tions, 294. 

Table  XXXVIII.  Water-consump- 
tion in  triple-expansion  engines, 
308. 

Table  XXXIX.     Tests  Parson's  tur- 
bine, 330. 
Table  XL.     Properties  of  ammonia, 

351. 
Table   XLI.     Cost    of    power-plants, 

390. 

Table   XLII.     Cost   of   steam   horse- 
power, 391. 
Table    XLIII.      Operating   expenses, 

steam,  392. 

Temperature  and  pressures,  310. 
Test,  triple-expansion  engine-,  309. 
Theoretical  efficiency,  180. 
Time  for  starting  engines,  344,  346. 


Trials  of  fuels,  44,  45. 

Triple  and   quadruple    engines,   308- 

316. 

Triple  valve-gear,  259. 
Turbine,  Curtiss,  333-339. 
Turbine,  De  Laval,  320-323. 
Turbine,  Dow,  324. 
Turbine-governor,  331. 
Turbine-nozles  and  -blades,  335,  337. 
Turbine,  Parson's,  325-330. 
Turbine,  Rateau,  339,  340. 
Turbine-step,  339. 
Turbine,  Wilkinson,  325. 
Turbine,  Zoelly,  341,  342. 
Turbines,  steam-,  317-347. 
Types  of  boilers,  41,  49-61. 
Types  of  superheaters,  160-168. 


U 


"Under"    and   "over   run"    engines, 
235. 


Vacuum-boiling,  28. 
Vacuum-dashpot,  285. 
Vacuum-installation,  128. 
Vacuum-pan,  28. 
Vacuum-pump,  126. 
Valve-gear,  234,  253-266. 
Valve-gear,  Corliss,  270-279,  286. 
Valve-gear,  floating,  257. 
Valve-gear,  Joy's,  260. 
Valve-gear,  reversing,  257. 
Valve-gear,   triple-expansion,   259. 
Valve  positions,   235-239. 
Valves  and  compound  cylinders,  295- 

297. 

Valves,  balanced,  239,  240. 
Valves,  double-ported,  241,  270. 
Valves,  piston-,  251,   252. 
Valves  with  riding-cover,  240. 
Vauclain  cylinders,  295,  296. 
Velocity  of  steam,  94,  95,  140,  143. 


INDEX 


485 


W 

Walschaert  valve-gear,   256. 
Warship  engines,  311-315. 
Waste  in  steam-making,  157. 
Water-consumption,  triple-expansion, 

308. 

Water-cooling  towers,  177. 
Water-gauge,  63,  65. 
Water  required  for  condensing,  122. 
Water-still,  28. 

Water  used  per  horse-power  hour,  199. 
Watertown  governor,  280. 
Watts  engine,  17. 


Wavy  expansion-lines,  204. 
Westinghouse  engine,  300. 
Wet  steam,  131. 
Wilkinson  turbine,  325. 
Worm-gear  elevator,  381. 

-X 

X,  dryness  of  steam,  143,  144. 


Zero  and  negative  lap,  237. 
Zoelly  turbine,  341,  342. 


INDEX  TO   ELECTRICAL    SECTION 


Active  material,  452. 
Alternating  and  direct  current,  419. 
Ammeter-connections,  445. 
Appliances  of  switchboard,  446. 
Arc-lamps,  425. 
Armature-balance,  442. 
Armature-coils  burnt  out,  437. 
Armature-drop,  427. 
Asphaltum  paint,  453. 

B 

Back  E.  M.  F.  calculated,  439. 
Back  E.  M.  F.  of  motor,  439. 
Back  field,  427. 
Bars   short-circuited,   432. 
Battery-room,  454. 
Branches,  the,  444. 
Brush-pressure,  435. 
Brushes,  heat  in  the,  436. 
Buckling  of  plates,  451. 


Carbon  filament,  455. 

Cause  of  heat  in  armature,  433. 

Central  station,  461. 

Centres  of  distribution,  444. 

Circuit-breaker,  the,  445. 

Circuits,  classification  of,  444. 

Classification  of  dynamos,  424. 

Closed  arcs,  425. 

Coils,  radiating  surface  of,  435. 

Collector-rings  and  commutator,  420. 

Commutator,  431. 

Commutator  and  collector-rings,  420. 

Commutator,  heat  in  the,  436. 

Commutator,  use  of,  422. 

Compensating  winding,  429. 

Compound-wound  dynamo,  regula- 
tion with  a,  428. 

Cost  and  durability  of  lamps,  458. 

Current-carrying  parts,  radiation  of, 
435. 

Currents,  parasitical,  436. 


Calculating  back  E.  M.  F.,  439. 
Calculation  of  E.  M.  F.,  421. 


Depreciation  in  gas  electric  plants,  466. 
Direct  and  alternating  current,  419. 
Distilling  coal,  466. 


486 


INDEX 


Distribution,  centres  of,  444. 
Drop  in  armature,  427. 
Durability  of  lamps,  458. 
Dynamo  fails  to  generate,  432. 
Dynamo,  operation  of  the,  419. 
Dynamo-regulation,  423. 
Dynamos,  classification  of,  424. 

E 

Efficiency  of  cells,  454. 
Efficiency  of  plants,  461. 
Electric  gas-engine  plants,  466. 
Electric  lamps,  456. 
Electric-light  equipments,  461. 
Electric  plants,  steam,  461. 
Electrical  efficiency,  439. 
Electromotive  force,  generation  of,  420. 
Elements  of  a  switchboard,  446. 
Enclosed  arc,  the,  459. 
Equipments,  electric-light,  461. 


Failure  to  generate,  dynamo's,  432. 

Faults,  testing  a  dynamo  for,  430. 

Faure  plate,  the,  449. 

Feeders,  444. 

Field  of  generator,  422. 

Filament,  the  carbon,  455. 

Flaming  arc,  the,  460. 


Incandescent  lamp,  the,  455. 


Jacobi's  principles,  437. 


Lamps,  cost  of,  458. 
Lamps,  durability  of,  458. 
Lamps,  electric,  456. 
Lightning-arrester,  the,  448. 
Lines  of  force,  421. 

M 

Magnetic  fringe,  432. 
Manufacturer's  guarantee,  465. 
Mercury  vapor-lamp,  462. 
Motor,  sparking  in  the,  440. 
Motor,  too  low  speed  of,  437. 
Motors,  humming  in,  442. 
Motors  in  service,  438. 
Motors,  noises  in,  442. 

N 

Nernst  lamp,  the,  457. 
No  field  to  motor,  440. 
Noises  in  motors,  442. 


Gas  electric  plants,  466. 
Gas-engine  plants,  466. 
Gas  plants,  producer-,  466. 
Generating  electromotive  force,  420. 
Generator-field,  422. 
Ground-detector,  the,  447. 
Grounded  armature-coils,  440. 
Grounds,  450. 

H 

Heat  in  the  commutator  and  brushes, 

436. 

Humming  in  motors,  442. 
Hydro-electric  plants,  466. 


0 

Old  lamps,  458. 

Open  arc,  candle-power,  460. 

Open  arcs,  425. 

Operation  of  the  dynamo,  419. 


Paint,  asphaltum,  453. 
Panel  board,  444. 
Parasitical  currents,  436. 
Parts  of  switchboard,  441. 
Pasted  plate,  452. 
Plante  plate,  the,  449. 


INDEX 


487 


Plants,  efficiency  of,  461. 
Plants,   water-power,   463. 
Plates  of  storage-battery,  449. 
Poles  alike,  433. 
Power-house,  461. 
Private  plant,  461. 
Producer-gas  plants,  466. 
Pure  lead  plate,  452. 

R 

Radiating  surface  of  coils,  435. 

Regulating  the  dynamo,  423. 

Regulation  with  a  compound-wound 
dynamo,  428. 

Regulation  with  a  series-wound  dy- 
namo, 425. 

Regulation  with  a  shunt-wound  dy- 
namo, 426. 

S 

Saving  with  enclosed  arc,  459. 
Series-wound  dynamo,  regulation  with 

a,  425. 
Shunt-wound  dynamo,  regulation  with 

a,  426. 

Similar  poles  in  a  dynamo,  433. 
Sparking,  431. 
Sparking  in  the  motor,  440. 
Steam  electric  plants,  461. 
Storage-batteries,  450 


Sulphating  of  plates,  451. 
Surface  of  coils,  438. 
Switchboard,  appliances  of,  446. 
Switchboard,  the,  441. 


Testing,  430. 

Testing  a  dynamo  for  faults,  430. 

The  dynamo,  419. 

The  incandescent  lamp,  455. 

The  open  arc,  460. 

Three  equipments,  461. 

Troubles  with  plates,  451. 

Turbine,  463. 

Types  of  motors  in  service,  438. 

Types  of  storage-batteries,  450. 


U 


Use  of  the  commutator,  422. 


Vacuum-tube  lamp,  462. 
Variable  source  of  power,  463. 
Voltmeter-connections,  445. 

W 

Water-power  plants,  463. 
Winding,  compensating,  429. 


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ject in  a  comprehensive  manner,  no  phase  of  it  being  omitted.  545  illustrations,  820 
pages.  Price,  $5.00. 

HISCOX.     Horseless  Vehicles,  Automobiles  and  Motor  Cycles,  Operated 
by  Steam,  Hydro-Carbon,  Electric,  and  Pneumatic  Motors 

A  practical  treatise  of  459  pages  and  316  illustrations  for  Automobilists,  Manufacturers, 
Capitalists,  Investors,  Promoters,  and  every  one  interested  in  the  development,  cr.re,  and 
use  of  the  Automobile. 

Nineteen  chapters.     Large  8 vo.     316  illustrations.     460  pages.     Cloth,  $1.50. 

HISCOX.     Mechanical  Movements,  Powers,  and  Devices 

This  work  of  400  pages  contains  1,800  specially  made  illustrations  with  descriptive 
text.  It  is  a  Dictionary  of  Mechanical  Movements,  Powers,  Devices,  and  Appliances, 
embracing  an  illustrated  description  of  the  greatest  variety  of  Mechanical  Movements  and 
Devices  in  any  language.  A  new  work  on  illustrated  Mechanics,  Mechanical  Movements 
and  Devices,  covering  nearly  the  whole  range  of  the  practical  and  inventive  field  for  the 
use  of  Machinists,  Mechanics,  Inventors,  Engineers,  Draughtsmen.  Students,  and  all  others 
interested  in  any  way  in  the  devising  and  operation  of  mechanical  works  of  any  kind.  $3.00. 


Publications  of  The  Norman  W.  Henley  Publishing  Co. 

HISCOX.     Mechanical  Appliances,  Mechanical  Movements  and  Novelties 
of  Construction 

The  many  editions  through  which  the  first  volume  of  "Mechanical  Movements"  has 
passed  are  more  than  a  sufficient  encouragement  to  warrant  the  publication  of  a  second 
volume  of  400  pages,  containing  1,000  larger  and  specially-made  illustrations,  which  are 
more  special  in  scope  than  those  in  the  first  volume,  inasmuch  as  they  deal  with  the  pecul- 
iar requirements  of  the  various  arts  and  manufactures,  and  more  detailed  in  their  ex- 
planations, because  of  the  greater  complexity  of  the  machinery  illustrated  and  described. 
$3,00. 

HISCOX.     Modern  Steam  Engineering  in  Theory  and  Practice 

This  book  has  been  specially  prepared  for  the  use  of  the  modern  steam  engineer,  the 
technical  students,  and  all  who  desire  the  latest  and  most  reliable  information  on  steam 
and  steam  boilers,  the  machinery  of  power,  the  steam  turbine,  electric  power  and  lighting 
plants,  etc.  450  octavo  pages,  400  detailed  engravings.  $3.00. 

KORNER.     Modern  Milling  Machines :   Their  Design,  Construction  and 
Operation 

This  work  of  304  pages  is  fully  illustrated  and  describes  and  illustrates  the  Milling 
Machine  from  its  early  conception  to  the  present  time.  $4.00. 

HORNER.     Practical  Metal  Turning 

A  work  covering  the  modern  practice  of  machining  metal  parts  in  the  lathe.  Fully 
illustrated.  $3.50. 

HORNER.     Tools  for  Machinists  and  Wood  Workers,  Including  Instru- 
ments of  Measurment 

A  practical  work  of  340  pages  fully  illustrated,  giving  a  general  description  and  classi- 
fication of  tools  for  machinists  and  woodworkers.  $3.50. 

Inventor's  Manual ;    How  to  Make  a  Patent  Pay 

This  is  a  book  designed  as  a  guide  to  inventors  in  perfecting  their  inventions,  taking 
out  their  patents  and  disposing  of  them.  119  pages.  Cloth,  $1.00. 

KRAUSS.     Linear  Perspective  Self-Taught 

The  underlying  principle  by  which  objects  may  be  correctly  represented  in  perspec- 
tive is  clearly  set  forth  in  this  book;  everything  relating  to  the  subject  is  shown  in  suitable 
diagrams,  accompanied  by  full  explanations  in  the  text.  Price  $2.50. 

LE  VAN.     Safety  Valves;    Their  History,  Invention,  and  Calculation 

Illustrated  by  69  engravings.      151  pages.     $1.50. 

LEWES  AND  BRAME.     Laboratory  Note  Book 

A  practical  treatise  prepared  for  the  Chemical  Student.    170  pages.     Cloth,  $1.00. 
MATHOT.     Modern  Gas  Engines  and  Producer  Gas  Plants 

A  practical  treatise  of  320  pages,  fully  illustrated  by  175  detailed  illustrations,  setting 
forth  the  principles  of  gas  engines  and  producer  design,  the  selection  and  installation  of 
an  engine,  conditions  of  perfect  operation,  producer-gas  engines  and  their  possibilities, 
the  care  of  gas  engines  and  producer-gas  plants,  with  a  chapter  on  volatile  hydrocarbon 
and  oil  engines.  $2.50. 

MEINHARDT.     Practical  Lettering  and  Spacing 

Shows  a  rapid  and  accurate  method  of  becoming  a  good  letterer  with  a  little  practice. 
Oblong.  Paper  cover.  60  cents. 

PARSELL  &  WEED.     Gas  Engine  Construction 

A  practical  treatise  describing  the  theory  and  principles  of  the  action  of  gas  engines 
of  various  types,  and  the  design  and  construction  of  a  half-horse-power  gas  engine,  with 
illustrations  of  the  work  in  actual  progress,  together  with  dimensioned  working  drawings 
giving  clearly  the  sizes  of  the  various  details.  .  Third  edition,  revised  and  enlarged.  Twen- 
ty-five chapters.  Large  8vo.  Handsomely  illustrated  and  bound.  300  pages.  $2.50. 

PERRIGO.     Modern  Machine  Shop  Construction,  Equipment  and  Man- 
agement 

The  only  work  published  that  describes  the  Modern  Machine  Shop  or  Manufacturing 
Plant  from  the  time  the  grass  is  growing  on  the  site  intended  for  it  until  the  finished  prod- 
uct is  shipped.  By  a  careful  study  of  its  chapters  the  practical  man  may  economically 
build,  efficiently  equip,  and  successfully  manage  the  modern  machine  shop  or  manufact- 
uring establishment.  Just  the  book  needed  by  those  contemplating  the  erection  of 
modern  shop  buildings,  the  rebuilding  and  reorganization  of  old  ones,  or  the  introduction 
of  Modern  Shop  Methods,  Time  and  Cost  Systems.  It  is  a  book  written  and  illustrated 
by  a  practical  shop  man  for  practical  shop  men  who  are  too  busy  to  read  theories  and  want 
tacts.  It  is  the  most  complete  all-around  book  of  its  kind  ever  published.  400  large 
quarto  pages,  225  original  and  specially-made  illustrations.  $5.00. 


Publications  of  The  Norman  W.  Henley  Publishing  Co. 

PERRIGO.      Modern  American  Lathe  Practice 

A  new  boqk  describing  and  illustrating  the  very  latest  practice  in  lathe  and  boring 
mill  operations,  as  well  as  the  construction  of  and  latest  developments  in  the  manufact- 
ure of  these  important  classes  of  machine  tools.  300  pages,  fully  illustrated.  $2.50. 

REAGAN,  JR.     Electrical    Engineers'    and   Students'  Chart  and   Hand- 
Book  of  the  Brush  Arc  Light  System 

Illustrated.     Bound  in  cloth,  with  celluloid  chart  in  pocket.     50  cents. 
SAUNIER.     Watchmaker's  Hand-Book 

Just  issued,  7th  edition.  Contains  498  pages  and  is  a  workshop  companion  for  those 
engaged  in  watchmaking  and  allied  mechanical  arts.  250  engravings  and  14  plates.  $3.00. 

SLOANE.     Electricity  Simplified 

The  object  of  "Electricity  Simplified"  is  to  make  the  subjecfas  plain  as  possible  and 
to  show  what  the  modern  conception  of  electricity  is.  158  pages.  Illustrated.  Twelfth 
edition.  $1.00. 

SLOANE.     How  to  Become  a  Successful  Electrician 

It  is  the  ambition  of  thousands  of  young  and  old  to  become  electrical  engineers.  Not 
every  one  is  prepared  to  spend  several  thousand  dollars  upon  a  college  course,  even  if  the 
three  of  .four  years  requisite  are  at  their  disposal.  It  is  possible  to  become  an  electrical 
engineer  without  this  sacrifice,  and  this  work  is  designed  to  tell  "How  to  Become  a  Suc- 
cessful Electrician"  without  the  outlay  usually  spent  in  acquiring  the  profession.  Twelfth 
edition.  189  pages.  Illustrated.  Cloth,  $1.00. 

SLOANE.     Arithmetic  of  Electricity 

A  practical  treatise  on  electrical  calculations  of  all  kinds,  reduced  to  a  series  of  rules, 
all  of  the  simplest  forms,  and  involving  only  ordinary  arithmetic ;  each  rule  illustrated<  by 
one  or  more  practical  problems,  with  detailed  solution  of  each  one.  Nineteenth  edition. 
Illustrated.  138  pages.  Cloth,  $1.00. 

SLOANE.     Electrician's  Handy  Book 

An  up-to-date  work  covering  the  subject  of  practical  electricity  in  all  its  branches, 
being  intended  for  the  every-day  working  'electrician.  The  latest  and  best  authority  on 
all  branches  of  applied  electricity.  Pocketbook  size.  Handsomely  bound  in  leather, 
with  title  and  edges  in  gold.  800  pages.  500  illustrations.  Price,  $3.50. 

SLOANE.     Electric  Toy  Making,  Dynamo  Building,  and  Electric  Motor 
Construction 

This  work  treats  of  the  making  at  home  of  electrical  toys,  electrical  apparatus,  motors, 
dynamos,  and  instruments  in  general,  and  is  designed  to  bring  within  the  reach  of  young 
and  old  the  manufacture  of  genuine  and  useful  electrical  appliances.  Eighteenth  edition. 
Fully  illustrated.  140  pages.  Cloth,  $1.00 

SLOANE.     Rubber  Hand  Stamps  and  the  Manipulation  of  India  Rubber 

A  practical  treatise  on  the  manufacture  of  all  kinds  of  rubber  articles.  146  pages. 
Second  edition.  Cloth.  $1.00. 

SLOANE.     Liquid  Air  and  the  Liquefaction  of  Gases 

Containing  the  full  theory  of  the  subject  and  giving  the  entire  history  of  liquefaction 
of  gases  from  the  earliest  times  to  the  present.  It  shows  how  liquid  air,  like  water,  is 
carried  hundreds  of  miles  and  is  handled  in  open  buckets.  It  tells  what  may  be  expected 
from  it  in  the  near  future.  365  pages,  with  many  illustrations.  Handsomely  bound  in 
buckram.  Second  edition.  $2.00. 

SLOANE.     Standard  Electrical  Dictionary 

A  practical  handbook  of  reference,  containing  definitions  of  about  5,000  distinct  words, 
terms,  and  phrases.  An  entirely  new  edition,  brought  up  to  date  and  greatly  enlarged. 
Complete,  concise,  convenient.  682  pages.  393  illustrations.  Handsomely  bound  in 
cloth.  8vo.  $3.00. 

STARBUCK.     Modern  Plumbing  Illustrated 

A  comprehensive  and  up-to-date  work  illustrating  and  describing  the  Drainage  and 
Ventilation  of  dwellings,  apartments,  and  public  buildings,  etc.  The  very  latest  and  most 
approved  methods  in  all  branches  of  sanitary  installation  are  given.  Adopted  by  the 
United  States  Government  in  its  sanitary  work  in  Cuba,  Porto  Rico,  and  the  Philippines, 
and  by  the  principal  boards  of  health  of  the  United  States  and  Canada.  The  standard 
book  for  master  plumbers,  architects,  builders,  plumbing  inspectors,  boards  of  health, 
boards  of  plumbing  examiners,  and  for  the  property  owner,  as  well  as  for  the  workman 
and  his  apprentice.  300  pages.  50  full-page  illustrations.  $4.00. 

USHER.     The  Modern  Machinist 

A  practical  treatise  embracing  the  most  approved  methods  of  modern  machine-shop 
practice,  and  the  applications  of  recent  improved  appliances,  tools,  and  devices  for  facili- 
tating, duplicating,  and  expediting  the  construction  of  machines  and  their  parts.  A  new 
book  from  cover  to  cover.  Fifth  edition.  257  engravings.  322  pages.  Cloth,  $2.50. 


Publications  of  The  Norman  W.  Henley  Publishing  Co. 

VAN  DERVOORT.     Modern  Machine  Shop  Tools ;  Their  Construction, 
Operation,  and  Manipulation,  Including  Both  Hand  and  Machine  Tools 

An  entirely  new  and  fully  illustrated  work  of  555  pages  and  673  illustrations,  describ- 
ing in  every  detail  the  construction,  operation,  and  manipulation  of  both  Hand  and  Machine 
Tools;  being  a  work  of  practical  instruction  in  all  classes  of  machine-shop  practice.  In- 
cluding chapters  on  filing,  fitting,  and  scraping  surfaces;  on  drills,  reamers,  taps,  and  dies; 
the  lathe  and  its  tools;  planers,  shapers,  and  their  tools;  milling  machines  and  cutters; 
gear  cutters  and  gear  cutting;  drilling  machines  and  drill  work;  grinding  machines  and 
their  work;  hardening  and  tempering;  gearing,  belting,  and  transmission  machinery' ;  useful 
data  and  tables.  Fourth  edition.  $4.00. 

WALLIS  -  TAYLOR.     Pocket  Book  of  Refrigeration  and  Ice  Making 

This  is  one  of  the  latest  and  most  comprehensive  reference  books  published  on  the  sub- 
ject of  refrigeration  and  cold  storage.  It  explains  the  properties  and  refrigerating  effect 
of  the  different  fluids  in  use,  the  management  of  refrigerating  machinery  and  the  construc- 
tion and  insulation  of  cold  rooms,  with  their  required  pipe  surface  for  different  degrees  of 
cold;  freezing  mixtures  and  non-freezing  brines,  temperatures  of  cold  rooms  for  all  kinds 
of  provisions;  cold-storage  charges  for  all  classes  of  goods,  ice-making  and  storage  of  ice, 
data  and  memoranda  for  constant  reference  by  refrigerating  engineers,  with  nearly  one 
hundred  tables  containing  valuable  references  to  every  fact  and  condition  required  in  the 
instalment  and  operation  of  a  refrigerating  plant.  $1.50. 

WOOD.     Walschaert  Locomotive  Valve  Gear 

The  only  work  issued  treating  of  this  subject  of  valve  motion.  150  pages,  illustrated. 
Cloth  $1.50. 

WOODWORTH.     American  Tool  Making   and   Interchangeable  Manu- 
facturing 

A  practical  treatise  of  560  pages,  containing  600  illustrations  on  the  designing,  con- 
structing, use,  and  installation  of  tools,  jigs,  fixtures,  devices,  special  appliances,  sheet-metal 
working  processes,  automatic  mechanisms,  and  labor-saving  contrivances;  together  with 
their  use  in  the  lathe,  milling  machine,  turret  lathe,  screw  machine,  boring  mill,  power 
press,  drill,  subpress,  drop  hammer,  etc.,  for  the  working  of  metals,  the  production  of  in- 
terchangeable machine  parts,  and  the  manufacture  of  repetition  articles  of  metal.  $4.00 

WOODWORTH.     Dies,  Their   Construction   and    Use   for   the   Modern 
Working  of  Sheet  Metals 

A  complete  treatise  of  384  pages  and  505  illustrations  upon  the  designing,  constructing, 
and  use  of  tools,  fixtures,  and  devices,  together  with  the  manner  in  which  they  should  be 
used  in  the  power  press,  for  the  cheap  and  rapid  production  of  the  great  variety  of  sheet- 
metal  articles  now  in  use.  It  is  designed  as  a  guide  to  the  production  of  sheet-metal  parts 
at  the  minimum  of  cost  with  the  maximum  of  output.  The  hardening  and  tempering  of 
Press  tools  and  the  classes  of  work  which  may  be  produced  to  the  best  advantage  by  the 
use  of  dies  in  the  Power  press  are  fully  treated. 

The  engravings  show  dies,  press  fixtures,  and  sheet-metal  working  devices,  from  the 
simplest  to  the  most  intricate,  and  the  descriptions  are  so  clear  and  practical  that  all  metal- 
working  mechanics  will  be  able  to  understand  how  to  design,  construct  and  use  them.  $3.00. 

WOODWORTH.     Hardening,    Tempering,    Annealing,  and   Forging  of 
Steel 

A  new  book  containing  special  directions  for  the  successful  hardening  and  tempering 
of  all  steel  tools.  Milling  cutters,  taps,  thread  dies,  reamers,  both  solid  and  shell,  hollow 
mills,  punches  and  dies,  and  all  kinds  of  sheet-metal  working  tools,  shear  blades,  saws, 
fine  cutlery  and  metal-cutting  tools  of  all  descriptions,  as  well  as  for  all  implements  of  steel, 
both  large  and  small,  the  simplest  and  most  satisfactory  hardening  and  tempering  processes 
are  presented.  The  uses  to  which  the  leading  brands  of  steel  may  be  adapted  are  con- 
cisely presented,  and  their  treatment  for  working  under  different  conditions  explained, 
as  are  also  the  special  methods  for  the  hardening  and  tempering  of  special  brands.  320 
pages.  250  illustrations.  $2.50. 

WOODWORTH.     Punches,  Dies  and  Tools  for  Manufacturing  in  Presses 

A  work  of  500  pages,  and  illustrated  by  nearly  700  engravings,  being  an  encyclopaedia 
of  die-making,  punch-making,  die-sinking,  sheet-metal  working,  and  making  of  special  tools, 
subpresses,  devices  and  mechanical  combinations  for  punching,  cutting,  bending,  forming, 
piercing,  drawing,  compressing,  and  assembling  sheet-metal  parts  and  also  articles  of  other 
materials  in  machine  tools.  $4.00. 

WRIGHT.     Electric  Furnaces  and  Their  Industrial  Application 

This  is  a  book  which  will  prove  of  interest  to  many  classes  of  people ;  the  manufacturer 
who  desires  to  know  what  product  can  be  manufactured  successfully  in  the  electric  furnace, 
the  chemist  who  wishes  to  post  himself  on  electro-chemistry,  and  the  student  of  science 
who  merely  looks  into  the  subject  from  curiosity.  The  book  is  not  so  scientific  as  to  be  of 
use  only  to  the  technologist,  nor  so  unscientific  as  to  suit  only  the  tyro  in  electro-chemistry ; 
it  is  a  practical  treatise  of  what  has  been  done,  and  of  what  is  being  done,  both  experi- 
mentally and  commercially,  with  the  electric  furnace.  288  pages.  $3.00. 


™"" 

1 


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KOV  19  1934 


201934 


JAN   39  1943 


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